Tinea Infections (Dermatophytosis)

1. Clinical Overview

Summary

Dermatophytosis (tinea infections) represents a group of superficial mycoses caused by keratinophilic fungi of the genera Trichophyton, Microsporum, and Epidermophyton. These organisms infect keratinized tissues—skin, hair, and nails—resulting in a spectrum of clinical presentations determined by anatomical location. [1,2]

Tinea infections constitute one of the most prevalent infectious dermatoses worldwide, affecting up to 20-25% of the global population at some point in their lifetime. [1] The clinical nomenclature follows anatomical convention: tinea corporis (body), tinea capitis (scalp), tinea pedis (feet), tinea cruris (groin), tinea manuum (hands), tinea unguium/onychomycosis (nails), tinea faciei (face), and tinea barbae (beard area). [3]

The characteristic morphology—an annular erythematous plaque with active, scaly peripheral edge and central clearing—earned the colloquial term "ringworm," though no helminthic organism is involved. Diagnosis combines clinical recognition with laboratory confirmation via potassium hydroxide (KOH) microscopy and fungal culture. Treatment stratifies by anatomical site: topical antifungals (terbinafine, azoles) suffice for most cutaneous infections, while scalp and nail involvement mandate systemic therapy. [4,5]

Clinical Pearls

Active Edge, Central Clearing: The pathognomonic annular morphology results from centrifugal fungal spread with host immune-mediated central healing.

Tinea Capitis Demands Oral Therapy: Topical agents cannot penetrate hair follicles adequately. Systemic antifungals (terbinafine, griseofulvin) are obligatory.

Kerion is an Immunological Emergency: This florid, suppurative inflammatory response requires urgent oral antifungals ± corticosteroids to prevent irreversible scarring alopecia. Despite its purulent appearance, it is NOT a bacterial abscess—incision is contraindicated.

Tinea Incognito: Misapplication of topical corticosteroids to dermatophyte infections suppresses inflammation, creating an atypical clinical picture that complicates diagnosis and perpetuates infection.

Two Feet, One Hand Syndrome: Bilateral tinea pedis with unilateral tinea manuum suggests chronic dermatophyte carriage and autoinoculation patterns.

---

2. Epidemiology

Global Burden and Prevalence

Dermatophytoses represent the most common fungal infections of humans globally, with prevalence estimates ranging from 20% to 25% in various populations. [1,6] Geographic, climatic, socioeconomic, and cultural factors significantly influence distribution patterns.

Causative Organisms

Dermatophytes are classified by ecological niche:

Risk Factors

Exam Detail: Host Factors:

• Age: Tinea capitis peaks in prepubertal children (sebaceous gland maturation post-puberty provides fungistatic free fatty acids); onychomycosis increases with age [11]
• Sex: Tinea cruris and pedis more common in males; tinea capitis shows no sex predilection
• Genetics: Some evidence for familial clustering, possibly related to cell-mediated immunity variations [16]
• Immunocompromise: HIV/AIDS, solid organ transplantation, chronic corticosteroid use predispose to extensive, refractory infections
• Diabetes mellitus: Impaired cellular immunity, neuropathy, peripheral vascular disease increase susceptibility
• Obesity: Intertriginous areas promote warm, moist environment

Environmental Factors:

• Warm, humid climates: Increase transmission and recurrence rates
• Occlusive footwear: Predisposes to tinea pedis
• Communal bathing facilities: Swimming pools, gyms, military barracks
• Contact sports: Wrestling, rugby (close skin contact)
• Occupational exposures: Agricultural workers (zoophilic organisms), industrial workers (occlusive protective equipment)
• Animal contact: Household pets (M. canis), livestock (T. verrucosum)
• Overcrowding: Schools, nurseries, institutional settings

---

3. Aetiology and Pathophysiology

Fungal Biology

Dermatophytes are filamentous fungi (moulds) that possess specialized enzymes—keratinases, elastases, and lipases—enabling digestion and invasion of keratinized tissues (stratum corneum, hair shafts, nails). [2] These organisms remain confined to non-viable keratinized structures; invasion of living dermis or systemic dissemination is exceedingly rare and occurs almost exclusively in profoundly immunocompromised hosts.

Pathogenesis

Exam Detail: Stage 1: Transmission and Adhesion

• Arthroconidia (asexual spores) transmitted via direct contact (human, animal) or fomites (towels, combs, floors)
• Adherence to keratinocytes mediated by fungal adhesins and surface proteins
• Requires minor skin trauma or maceration to breach intact stratum corneum

Stage 2: Keratin Invasion

• Secretion of keratinases, proteases, and lipases degrades keratin matrix
• Fungal hyphae penetrate stratum corneum, invading outward in centrifugal pattern
• Keratin serves as primary nutrient source for fungal metabolism

Stage 3: Host Immune Response

• Innate immunity: Epidermal keratinocytes recognize fungal pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs), triggering cytokine release (IL-1, IL-6, TNF-α)
• Adaptive immunity: T-helper 1 (Th1) cell-mediated response critical for fungal clearance [17]
• Delayed-type hypersensitivity (DTH) reaction contributes to inflammatory changes, scaling, and pruritus
• Zoophilic organisms typically elicit more vigorous inflammatory responses than anthropophilic species

Stage 4: Clinical Manifestation

• Annular morphology: Centrifugal spread with active peripheral edge (viable fungal elements) and central clearing (immune-mediated resolution)
• Scaling: Accelerated keratinocyte turnover and desquamation
• Erythema: Inflammatory mediator-induced vasodilation
• Pruritus: Histamine release and cytokine effects on cutaneous nerve endings

Special Patterns:

• Kerion formation: Intense cell-mediated immune response (especially to zoophilic organisms) produces boggy, suppurative inflammatory mass mimicking bacterial abscess [18]
• Majocchi granuloma: Follicular and perifollicular dermatophyte invasion (typically T. rubrum) causing granulomatous inflammation; associated with immunosuppression or topical corticosteroid use

---

4. Clinical Presentations by Anatomical Site

Tinea Corporis (Body - "Ringworm")

Classic Presentation:

• Morphology: Annular (ring-shaped) erythematous plaques with well-demarcated, raised, scaly peripheral edge
• Central clearing: Relatively normal-appearing skin within the ring as peripheral expansion continues
• Distribution: Any non-hair-bearing skin surface; trunk and extremities most common
• Symptoms: Pruritic (often moderate to severe)
• Variants:
  • Multiple confluent rings
  • Vesicular or pustular edge (more inflammatory response)
  • Polycyclic patterns (overlapping rings)

Special Situations:

• Tinea corporis gladiatorum: Outbreaks in wrestlers and contact sport athletes; caused by T. tonsurans [19]
• Majocchi granuloma: Folliculitis and perifolliculitis; papules and plaques, often on legs after shaving

Differential Diagnosis:

• Nummular eczema (coin-shaped, no active edge, more eczematous scale)
• Psoriasis (well-demarcated, silvery scale, extensor surfaces, nail changes)
• Pityriasis rosea (herald patch, Christmas tree distribution, no active edge)
• Granuloma annulare (annular papules, no scale, flesh-colored)
• Erythema migrans (Lyme disease—expanding erythema, no scale, history of tick exposure)

Tinea Pedis (Feet - "Athlete's Foot")

Tinea pedis represents the most common dermatophyte infection in adults, particularly in temperate climates. [7] Three clinical variants exist:

Complications:

• Bacterial superinfection: Fissures provide portal of entry for Streptococcus pyogenes or Staphylococcus aureus, leading to cellulitis or erysipelas
• Id reaction (dermatophytid): Immunological reaction to circulating fungal antigens, manifesting as symmetric vesicular eruption on hands, trunk, or extremities distant from primary infection site

Differential Diagnosis:

• Contact dermatitis (irritant or allergic; often bilateral, history of exposure)
• Palmoplantar psoriasis (well-demarcated, thick scale, nail pitting)
• Dyshidrotic eczema (vesicles on palms/soles, symmetric, no interdigital involvement)
• Juvenile plantar dermatosis (children, shiny erythema of weight-bearing areas)

Tinea Capitis (Scalp)

Tinea capitis predominantly affects prepubertal children (peak age 3-7 years), with higher prevalence in Afro-Caribbean populations. [9,14] Post-pubertal individuals rarely develop tinea capitis due to fungistatic properties of sebaceous secretions (medium-chain fatty acids).

Clinical Patterns:

1. Non-inflammatory (Seborrheic) Type:

   • Patchy alopecia with gray, adherent scale
   • "Black dot" pattern: broken hairs at scalp surface (T. tonsurans)
   • Minimal inflammation
   • Often misdiagnosed as seborrheic dermatitis or dandruff

2. Inflammatory Type:

   • Erythematous, scaly plaques with pustules
   • Painful, tender
   • Lymphadenopathy (posterior cervical, occipital)

3. Kerion:

   • Boggy, edematous, purulent mass studded with follicular pustules
   • Exquisitely tender
   • Serous or purulent discharge
   • Represents intense delayed-type hypersensitivity reaction (NOT bacterial abscess)
   • Risk: Permanent scarring alopecia if treatment delayed [18]
   • Often associated with zoophilic organisms (M. canis, T. verrucosum)

4. Favus (Rare):

   • Caused by T. schoenleinii
   • Yellow cup-shaped crusts (scutula) on scalp
   • Mouse-like odor
   • Severe scarring alopecia
   • Rare in developed countries

Wood's Lamp Fluorescence:

• Microsporum species (M. canis, M. audouinii): Bright green-yellow fluorescence
• Trichophyton species (T. tonsurans, T. violaceum): No fluorescence
• Modern utility limited as T. tonsurans (non-fluorescent) now predominates in UK/USA [14]

Differential Diagnosis:

• Alopecia areata (smooth, non-scarring patches, no scale, exclamation mark hairs)
• Seborrheic dermatitis (diffuse scale, no alopecia, greasy rather than dry scale)
• Psoriasis (well-demarcated, thick silvery scale, no alopecia)
• Bacterial folliculitis (pustules, no significant alopecia)
• Trichotillomania (bizarre, geometric patterns, hairs of varying lengths)

Tinea Cruris (Groin - "Jock Itch")

Tinea cruris occurs predominantly in adolescent and adult males, favored by warm, humid conditions and occlusive clothing. [10]

Clinical Features:

• Distribution: Erythematous, scaly plaques in inguinal creases, extending onto medial thighs and buttocks
• Key diagnostic feature: Spares scrotum (distinguishes from candidal intertrigo, which involves scrotum)
• Morphology: Well-demarcated plaques with active, raised scaly edge
• Symptoms: Pruritus (often significant)
• Chronic cases: Post-inflammatory hyperpigmentation

Differential Diagnosis:

Tinea Unguium / Onychomycosis (Nails)

Onychomycosis affects 2-8% of the general population, increasing to 20-50% in individuals over 70 years. [11] Toenails are affected more frequently than fingernails (10:1 ratio).

Clinical Subtypes:

Risk Factors (Specific to Onychomycosis):

• Increasing age
• Peripheral vascular disease
• Diabetes mellitus
• Psoriasis
• Immunosuppression
• Family history
• Tinea pedis
• Trauma
• Communal bathing

Differential Diagnosis:

• Psoriatic nail disease (pitting, oil drop sign, salmon patches, onycholysis)
• Lichen planus (thinning, ridging, pterygium, 20-nail dystrophy)
• Chronic paronychia (Candida)
• Traumatic onychodystrophy
• Yellow nail syndrome
• Bacterial/Pseudomonal infection (green discoloration)

Tinea Manuum (Hands)

Tinea manuum is relatively uncommon, accounting for approximately 1-2% of dermatophytoses. [12]

Classic Pattern: "Two Feet, One Hand Syndrome"

• Bilateral tinea pedis with unilateral tinea manuum
• Dominant hand typically affected (autoinoculation from scratching feet)
• Suggests chronic dermatophyte carriage

Clinical Features:

• Unilateral (key feature)
• Diffuse fine scale on palm ("powdery" appearance)
• Accentuation of palmar creases
• Hyperkeratosis
• May extend to dorsum with annular plaques
• Often subtle and asymptomatic

Differential Diagnosis:

• Contact dermatitis (bilateral, history of irritant/allergen exposure)
• Palmoplantar psoriasis (bilateral, well-demarcated, thick scale)
• Hyperkeratotic eczema (bilateral, more pruritic)

Tinea Faciei (Face)

Tinea faciei is often misdiagnosed due to atypical appearance, particularly when modified by topical corticosteroid use ("tinea incognito"). [22]

Clinical Features:

• Erythematous patches or plaques on face (excluding beard area)
• May be annular with scaly edge or diffuse
• Asymmetric distribution
• Photosensitivity sometimes reported
• Minimal scale in some cases

Tinea Incognito:

• Results from topical corticosteroid application to undiagnosed tinea
• Suppresses inflammation, masking typical features
• Creates atypical morphology: less scale, less defined border, persistent erythema
• May spread more extensively
• Diagnosis requires high index of suspicion

Differential Diagnosis:

• Seborrheic dermatitis (symmetric, eyebrows and nasolabial folds)
• Rosacea (central face, telangiectasia, papulopustules)
• Lupus erythematosus (malar distribution, photosensitivity, systemic features)
• Eczema (bilateral, less well-demarcated)
• Polymorphous light eruption (photodistribution, seasonal)

Tinea Barbae (Beard Area)

Rare; affects males in beard and moustache area. Similar presentations to tinea capitis: superficial scaling to deep kerion-like masses. Differential includes bacterial folliculitis and pseudofolliculitis barbae.

---

5. Investigations

Clinical Diagnosis

Many tinea infections are diagnosed clinically based on characteristic morphology and distribution. However, laboratory confirmation is recommended in the following scenarios:

• Atypical presentation
• Treatment failure
• Before initiating prolonged systemic therapy (especially for onychomycosis)
• Medicolegal considerations
• Immunocompromised patients
• Suspected tinea incognito

Mycological Sampling Techniques

Exam Detail: Skin Scrapings (Tinea Corporis, Cruris, Pedis, Manuum, Faciei):

1. Clean area with 70% alcohol to remove surface contaminants
2. Scrape active edge of lesion (highest fungal load) with #15 scalpel blade or edge of glass slide
3. Collect scales onto black paper or directly into sterile container
4. Ensure adequate sample volume (rice grain-sized minimum)

Hair Sampling (Tinea Capitis):

1. Brush sampling (Mackenzie toothbrush technique): Rub sterile toothbrush vigorously over affected scalp area; most sensitive method [23]
2. Plucked hairs: Use forceps to epilate 10-20 hairs with roots from affected area (broken "black dot" hairs ideal)
3. Scalp scale: Scrape scales from affected areas

Nail Sampling (Onychomycosis):

1. Clean nail surface with 70% alcohol
2. Best sample site depends on subtype:
   • DLSO: Clip distal nail, collect subungual debris from nail bed
   • SWO: Scrape superficial nail plate
   • PSO: Remove superficial layers, sample deep nail plate near cuticle
3. Collect adequate material (multiple nail clippings preferred)
4. Sample before starting antifungal therapy (if possible)

Laboratory Tests

Wood's Lamp (Ultraviolet Light) Examination

• Wavelength: 365 nm (long-wave UV)
• Mechanism: Certain fungal metabolites (pteridines) fluoresce
• Positive Findings:
  • "Microsporum canis, M. audouinii: Bright green-yellow fluorescence of infected hair shafts"
  • "Microsporum ferrugineum: Green fluorescence"
• Negative (No Fluorescence):
  • Trichophyton tonsurans (most common tinea capitis in UK/USA)
  • Trichophyton violaceum
  • Trichophyton rubrum
• Clinical Utility: Limited in modern practice due to predominance of non-fluorescent organisms; may help identify M. canis in suspected zoonotic transmission

Other Uses:

• Erythrasma: Coral-pink fluorescence (Corynebacterium minutissimum produces porphyrins)
• Pityriasis versicolor: Yellow-gold fluorescence (Malassezia species)

---

6. Classification and Grading

Dermatophytoses are classified primarily by anatomical location and causative organism, rather than severity staging systems.

Anatomical Classification

Organism Classification (Ecological Niche)

---

7. Management

Management of tinea infections stratifies by anatomical location, extent of infection, and organism characteristics. The fundamental principle: topical therapy suffices for limited cutaneous infections; systemic therapy required for hair-bearing areas (scalp, beard), nails, extensive cutaneous involvement, or immunocompromised hosts.

Management Algorithm

SUSPECTED TINEA INFECTION
         ↓
CLINICAL ASSESSMENT
- Anatomical site
- Extent (localized vs. extensive)
- Inflammatory vs. non-inflammatory
- Host factors (age, immunocompromise)
         ↓
CONFIRM DIAGNOSIS (if uncertain)
- Skin/hair/nail sampling
- KOH microscopy ± fungal culture
         ↓
SITE-SPECIFIC MANAGEMENT
         ↓
┌────────────────────────┬──────────────────────────┬────────────────────────┐
│                        │                          │                        │
TINEA CORPORIS/         TINEA CAPITIS             TINEA UNGUIUM
CRURIS/PEDIS/MANUUM/    (Scalp/Hair)              (Nails)
FACIEI                                             
(Skin Only)                                        
│                        │                          │
↓                        ↓                          ↓
LOCALIZED:              ALWAYS SYSTEMIC:          SYSTEMIC:
Topical Antifungal      - Terbinafine PO          - Terbinafine PO
- Terbinafine 1%          (Trichophyton)            (3mo fingers,
  cream BD 1-2wk          250mg OD 4-6wk            6mo toes)
- OR Clotrimazole         (children: dose by      - OR Itraconazole
  1% cream BD 2-4wk       weight)                   pulse therapy
- Continue 1 week       - OR Griseofulvin         - OR Fluconazole
  after clinical          (Microsporum)           ↓
  resolution              10-15mg/kg/day          Monitor LFTs if
↓                         6-8wk                   prolonged use
EXTENSIVE/              PLUS:                     Counsel re:
RESISTANT:              - Antifungal              - Slow response
Add Oral Antifungal       shampoo (ketoconazole   - Nail appearance
- Terbinafine PO          2%, selenium sulfide)     lags mycological
  2-4 weeks               2x/week (reduce           cure
- OR Itraconazole         spore shedding)         - Recurrence risk
  1 week               ↓
                      KERION:
                      - Oral antifungal
                        (as above)
                      - PLUS Prednisolone
                        0.5-1mg/kg/day
                        2 weeks
                      - DO NOT INCISE
                      ↓
                      ADJUNCTIVE:
                      - Screen/treat contacts
                      - Treat animal sources
                      - Hygiene education

Topical Antifungal Therapy

Exam Detail: Indications:

• Localized tinea corporis, cruris, pedis, manuum, faciei
• Adjunctive therapy in tinea capitis (antifungal shampoo)
• Not effective as monotherapy for tinea capitis or onychomycosis

Agent Selection and Dosing:

Application Technique:

• Apply to affected area PLUS 2-3 cm beyond visible lesion (subclinical extension common)
• Continue for 1 week after clinical resolution (prevent relapse)
• Counsel on adherence (premature discontinuation common cause of treatment failure)

Treatment Failure:

• Confirm diagnosis (repeat mycology)
• Assess adherence
• Consider resistant organism or alternative diagnosis
• Escalate to systemic therapy

Systemic Antifungal Therapy

Indications:

• Tinea capitis (mandatory)
• Tinea barbae (mandatory)
• Onychomycosis (mandatory)
• Extensive tinea corporis/cruris/pedis (> 10% body surface area)
• Treatment failure with topical therapy
• Immunocompromised host
• Majocchi granuloma

Exam Detail: | Agent | Dosing | Duration | Mechanism | Indications | Monitoring | Contraindications/Cautions | Evidence | |-------|--------|----------|-----------|-------------|------------|---------------------------|----------| | Terbinafine | Adults: 250mg PO OD
Children: less than 20 kg: 62.5mg OD
greater than 20-40 kg: 125mg OD
Over 40 kg: 250mg OD | Tinea capitis: 4-6 weeks
Fingernails: 6 weeks
Toenails: 12 weeks | Allylamine: inhibits squalene epoxidase → fungicidal | First-line for Trichophyton infections (tinea capitis, onychomycosis) [26] | Baseline LFTs; repeat if > 6 weeks therapy or symptoms | Liver disease, pregnancy (Cat B), drug interactions (CYP2D6 substrate) | Superior to griseofulvin for Trichophyton; [26] 70-80% cure rate onychomycosis [11] | | Griseofulvin | Microsize: 10-20mg/kg/day (max 1000mg)
Ultramicrosize: 5-15mg/kg/day | Tinea capitis: 6-12 weeks (Microsporum may require longer) | Disrupts fungal microtubule function → fungistatic | Tinea capitis (especially Microsporum); historical first-line [27] | CBC, LFTs periodically if prolonged | Liver disease, porphyria, pregnancy (Cat X - teratogenic), lupus | Longer duration required vs. terbinafine; less effective for Trichophyton [26] | | Itraconazole | Continuous: 200mg OD
Pulse: 200mg BD x 1 week per month | Tinea capitis: 4-6 weeks continuous
Fingernails: 2 pulses
Toenails: 3-4 pulses | Azole: inhibits ergosterol synthesis → fungistatic | Alternative for tinea capitis (Microsporum); onychomycosis pulse therapy [28] | LFTs, cardiac function (avoid in CHF) | Heart failure, liver disease, pregnancy (Cat C), multiple drug interactions (CYP3A4 inhibitor) | Pulse therapy: 60-70% cure rate onychomycosis; [28] effective for Microsporum | | Fluconazole | Tinea capitis: 6mg/kg/day (max 300mg)
Onychomycosis: 150-300mg once weekly | Tinea capitis: 3-6 weeks
Onychomycosis: 6-12 months | Azole: inhibits ergosterol synthesis → fungistatic | Alternative agent; less evidence than terbinafine/griseofulvin | LFTs if prolonged therapy | Liver disease, pregnancy (Cat D if high-dose), drug interactions (CYP3A4, 2C9 inhibitor) | Limited evidence; convenience of once-weekly dosing for onychomycosis |

Drug Interactions (Key Examples):

• Terbinafine: CYP2D6 substrate/inhibitor (TCAs, SSRIs, beta-blockers, antiarrhythmics)
• Griseofulvin: CYP450 inducer (warfarin, OCPs—reduce efficacy)
• Itraconazole: CYP3A4 inhibitor (statins, calcium channel blockers, warfarin, many others)
• Fluconazole: CYP2C9, 3A4 inhibitor (warfarin, phenytoin, statins)

Monitoring Recommendations:

• Baseline LFTs before systemic therapy
• Repeat LFTs if therapy > 6 weeks OR patient develops symptoms (nausea, vomiting, jaundice, dark urine, abdominal pain)
• Discontinue if ALT > 3x upper limit of normal

Special Scenarios

Kerion Management:

• Oral antifungal therapy (terbinafine or griseofulvin as per tinea capitis dosing)
• Corticosteroid therapy: Prednisolone 0.5-1mg/kg/day for 2 weeks (reduces inflammation, minimizes scarring alopecia) [18]
• DO NOT incise or drain (common error—kerion is NOT a bacterial abscess; incision worsens scarring)
• Bacterial superinfection occasionally occurs; if suspected (fever, systemic symptoms, increased purulence), add antibiotics (flucloxacillin or cephalexin)
• Close follow-up to monitor response and minimize permanent alopecia

Tinea Pedis - Adjunctive Measures:

• Foot hygiene: Daily washing and thorough drying, especially interdigital spaces
• Breathable footwear (leather preferred over synthetic)
• Cotton socks changed daily
• Antifungal powders (miconazole, tolnaftate) in shoes
• Rotate footwear (allow drying between uses)
• Treat concurrent onychomycosis (reservoir for recurrence)
• Topical antibacterials if bacterial superinfection

Onychomycosis - Adjunctive Therapies:

• Nail debridement: Manual filing or chemical (urea 40%) to reduce fungal load and enhance drug penetration
• Antifungal nail lacquer: Ciclopirox 8% or amorolfine 5% (limited efficacy as monotherapy; cure rates 5-10%; [11] may use adjunctively with oral therapy)
• Laser therapy: Emerging modality; limited evidence for efficacy

Tinea Capitis - Adjunctive Measures and Public Health Considerations:

• Antifungal shampoo: Ketoconazole 2% or selenium sulfide 2.5% twice weekly reduces spore shedding and transmission (does NOT treat infection) [29]
• Screen and treat contacts: Household members, classmates (carrier state common)
• No school exclusion once treatment started (varies by local policy)
• Treat animal sources: Examine household pets; veterinary evaluation and treatment if M. canis suspected
• Hygiene education: Avoid sharing combs, brushes, hats, pillowcases

Pregnancy and Lactation

• Topical antifungals: Generally safe (minimal systemic absorption)
• Systemic antifungals:
  • "Terbinafine: Category B (limited human data; weigh risks/benefits; generally deferred if possible)"
  • "Griseofulvin: Category X (teratogenic in animal studies; contraindicated)"
  • "Fluconazole: Category D (high-dose associated with birth defects; avoid)"
  • "Itraconazole: Category C (avoid if possible)"
• Management strategy: Defer systemic therapy for non-urgent indications (e.g., onychomycosis) until after pregnancy/lactation; topical therapy for cutaneous infections

Immunocompromised Patients

• Higher risk of extensive, atypical, and refractory infections
• Longer treatment duration often required
• Monitor closely for treatment failure
• Consider antifungal susceptibility testing if available
• Proximal subungual onychomycosis (PSO) in HIV warrants evaluation for immunodeficiency

---

8. Complications

---

9. Prognosis and Outcomes

Tinea Corporis, Cruris, Pedis, Manuum

• Cure rates with topical therapy: 70-90% [5]
• Cure rates with systemic therapy (extensive/refractory): > 90%
• Recurrence rates: 20-25% (tinea pedis highest) [7]
• Time to resolution: Typically 2-4 weeks with appropriate therapy
• Prognosis: Excellent with treatment; no long-term sequelae if uncomplicated

Tinea Capitis

• Cure rates with oral therapy: 85-95% [26,27]
• Scarring alopecia risk: 10-20% if kerion inadequately treated [18]
• Post-inflammatory hyperpigmentation: Common, resolves over months
• Recurrence: 5-10% (reinfection from environmental/human reservoir)
• Prognosis: Excellent if treated promptly; permanent alopecia if kerion management delayed

Onychomycosis

• Cure rates:
  • "Terbinafine (toenails): 60-70% mycological cure, 35-50% complete cure (clinical + mycological) [11]"
  • "Terbinafine (fingernails): 70-80% complete cure"
  • "Itraconazole pulse therapy: 60-70% mycological cure [28]"
• Recurrence rates: 10-30% at 1-3 years [11]
• Time to clinical cure: Lags mycological cure; fingernails 4-6 months, toenails 9-12 months (nail growth rate)
• Prognosis: Challenging; lower cure rates than cutaneous infections; toenails particularly difficult; high recurrence; quality of life impact

Factors Associated with Poor Prognosis

• Advanced age (onychomycosis)
• Peripheral vascular disease
• Diabetes mellitus
• Immunosuppression
• Extensive nail involvement (> 50% nail plate, lateral disease, matrix involvement)
• Non-adherence to therapy
• Reinfection from environment (persistent tinea pedis, contaminated footwear)

---

10. Prevention and Public Health

Primary Prevention

Individual Measures:

• Maintain good personal hygiene (daily washing, thorough drying)
• Avoid walking barefoot in communal areas (gyms, pools, locker rooms)
• Wear protective footwear (flip-flops) in public showers
• Change socks daily; wear breathable fabrics (cotton)
• Rotate footwear to allow drying
• Avoid sharing personal items (towels, combs, brushes, hats, clothing)
• Inspect and treat household pets (veterinary consultation if skin lesions)
• Wash hands after handling animals

Environmental Measures:

• Regular cleaning and disinfection of communal bathing facilities
• Adequate ventilation in locker rooms, gyms
• Education in schools, sports teams, military regarding transmission

Secondary Prevention (Screening)

• No formal screening programs exist for general population
• Targeted screening in outbreak settings:
  • "Tinea capitis: Screen household contacts, classmates"
  • "Tinea corporis gladiatorum: Screen wrestling teams, contact sport athletes"

Outbreak Management (Tinea Capitis)

• Identify index case(s)
• Screen household contacts and close contacts (school, nursery)
• Culture positive carriers even if asymptomatic
• Treat carriers with antifungal shampoo (reduce transmission) ± oral therapy
• Environmental decontamination (launder bedding, hats; clean combs/brushes)
• Veterinary assessment of household pets
• Education regarding transmission and hygiene
• No school exclusion necessary once treatment initiated (policy varies by region)

---

11. Key Guidelines and Evidence

Major Clinical Guidelines

Landmark Studies and Evidence

1. Terbinafine vs. Griseofulvin for Tinea Capitis: Gupta et al. meta-analysis demonstrated terbinafine superiority over griseofulvin for Trichophyton infections (shorter duration, higher cure rates), but griseofulvin remained effective for Microsporum. [26]

2. Pulse Itraconazole for Onychomycosis: De Backer et al. showed 70% mycological cure rate with itraconazole pulse therapy, comparable to continuous terbinafine, with potential cost savings. [28]

3. Topical Terbinafine vs. Azoles: Systematic reviews confirm allylamine superiority (terbinafine, butenafine) over azoles for dermatophyte infections, with shorter treatment duration required. [5]

4. Antifungal Shampoo Adjunct in Tinea Capitis: Reduced spore shedding and transmission demonstrated with ketoconazole 2% shampoo, though not curative as monotherapy. [29]

---

12. Examination Focus

Common MRCP/Dermatology Exam Scenarios

Exam Detail: Scenario 1: Annular Rash

Stem: "A 25-year-old man presents with a 2-week history of an itchy rash on his left forearm. Examination reveals a 3cm annular erythematous plaque with a scaly raised edge and central clearing. What is the most likely diagnosis?"

Model Answer: "The most likely diagnosis is tinea corporis (ringworm). The key features supporting this are: (1) annular morphology with active scaly edge and central clearing—pathognomonic for dermatophyte infection; (2) pruritic; (3) localized to forearm. To confirm, I would perform skin scrapings from the active edge for KOH microscopy and fungal culture. Treatment would be topical terbinafine 1% cream applied twice daily for 1-2 weeks, extending 2-3cm beyond the visible lesion."

---

Scenario 2: Treatment Failure

Stem: "A 6-year-old girl with patchy scalp alopecia and scaling has been treated with topical clotrimazole for 4 weeks without improvement. What is the most appropriate next step?"

Model Answer: "The diagnosis is likely tinea capitis. Topical antifungals are ineffective for tinea capitis because they cannot penetrate the hair follicle adequately. This is a key teaching point and common exam question. The treatment failure is due to inappropriate therapy rather than resistant organism. Management requires: (1) Discontinue topical therapy; (2) Obtain scalp brushings/plucked hairs for mycology (KOH + culture) to confirm diagnosis and identify organism; (3) Commence oral antifungal therapy—terbinafine (first-line for Trichophyton) or griseofulvin (for Microsporum), dosed by weight for 4-6 weeks minimum; (4) Add antifungal shampoo (ketoconazole 2% twice weekly) to reduce spore shedding; (5) Screen household contacts; (6) Examine pets for fungal lesions."

---

Scenario 3: Kerion

Stem: "An 8-year-old boy presents with a 5cm tender, boggy, purulent mass on his scalp with surrounding alopecia. The lesion developed over 2 weeks. He owns a cat. Diagnosis and management?"

Model Answer: "This is a kerion—a severe inflammatory reaction to dermatophyte infection, most commonly caused by zoophilic organisms like Microsporum canis (consistent with cat ownership). Key features: boggy, tender scalp mass with pustules and alopecia. This is NOT a bacterial abscess—incision and drainage are contraindicated and will worsen scarring. The purulent appearance reflects intense delayed-type hypersensitivity rather than bacterial infection. Management: (1) Oral antifungal therapy (griseofulvin 10-15mg/kg/day for 6-8 weeks, preferred for Microsporum; or terbinafine if Trichophyton); (2) Oral corticosteroids (prednisolone 0.5-1mg/kg/day for 2 weeks) to reduce inflammation and minimize permanent scarring alopecia; (3) Antifungal shampoo; (4) Veterinary assessment of cat and treatment if infected; (5) Close follow-up. Warn family that despite treatment, some permanent scarring alopecia may occur if follicular destruction has occurred."

---

Scenario 4: Tinea Cruris vs. Candida

Stem: "A 30-year-old obese man presents with an itchy groin rash. How would you differentiate tinea cruris from candidal intertrigo?"

Model Answer: "Key distinguishing features:

Tinea cruris:

• Spares scrotum (critical differentiator)
• Well-demarcated plaques with active scaly edge
• Extends onto medial thighs
• More pruritic
• KOH: septate hyphae

Candidal intertrigo:

• Involves scrotum (moist, occluded area favors Candida)
• Beefy-red, moist, macerated appearance
• Satellite pustules beyond main rash (characteristic)
• Less well-demarcated
• KOH: pseudohyphae and budding yeasts

Treatment differs: tinea cruris responds to terbinafine or azole creams; candidiasis requires azole (clotrimazole, miconazole) with attention to moisture control and possibly combination with hydrocortisone initially for inflammation."

---

Scenario 5: Onychomycosis Pre-Treatment

Stem: "A 65-year-old diabetic man requests treatment for thickened, discolored toenails present for several years. What investigations would you perform before initiating treatment?"

Model Answer: "Before commencing systemic antifungal therapy for presumed onychomycosis, I would:

Investigations:

1. Mycological confirmation: Nail clipping and subungual debris for KOH microscopy and fungal culture. This is essential before starting prolonged oral therapy because: (a) confirms diagnosis (psoriatic nail disease, lichen planus, traumatic dystrophy can mimic); (b) identifies organism (dermatophyte vs. yeast vs. mold—treatment differs); (c) provides baseline for monitoring response.

2. Baseline LFTs: Oral terbinafine (first-line) requires 12 weeks for toenails; monitor hepatotoxicity risk.

3. Drug interaction review: Terbinafine is CYP2D6 substrate/inhibitor; check concurrent medications.

4. Assess extent: If > 50% nail involvement, lateral disease, or matrix involvement—poorer prognosis; counsel regarding lower cure rates.

Rationale: Up to 50% of dystrophic nails are NOT fungal; [11] systemic therapy has risks (hepatotoxicity, drug interactions, cost); confirmation prevents unnecessary treatment."

Viva Voce Points

Viva Point: Opening Statement: "Dermatophytosis, commonly known as tinea or ringworm, is a superficial fungal infection of keratinized tissues—skin, hair, and nails—caused by filamentous fungi of the genera Trichophyton, Microsporum, and Epidermophyton. It is one of the most common infectious skin conditions globally, with prevalence estimates of 20-25%. Clinical nomenclature follows anatomical location: tinea corporis for body, tinea capitis for scalp, tinea pedis for feet, and so forth."

Key Facts to Mention:

1. Organism classification: Anthropophilic (human-to-human, e.g., T. rubrum), zoophilic (animal-to-human, e.g., M. canis), geophilic (soil-to-human, rare)
2. Most common organisms: T. rubrum (globally dominant for skin/nail infections), T. tonsurans (tinea capitis in UK/USA)
3. Pathognomonic morphology: Annular plaque with active scaly edge and central clearing
4. Diagnosis: Clinical + mycological confirmation (KOH microscopy, fungal culture)
5. Treatment principle: Topical antifungals for skin; oral antifungals mandatory for hair/nails
6. Wood's lamp: Microsporum fluoresces green; Trichophyton does not
7. Kerion: Inflammatory scalp mass requiring oral antifungals + corticosteroids (NOT incision)

Common Follow-Up Questions:

• "Why doesn't topical therapy work for tinea capitis?" → Cannot penetrate hair follicle
• "Which antifungal for tinea capitis?" → Terbinafine (Trichophyton), griseofulvin (Microsporum)
• "How do you differentiate tinea cruris from candidiasis?" → Tinea spares scrotum; candida involves it
• "What is tinea incognito?" → Atypical presentation from topical corticosteroid misuse

Common Exam Mistakes

❌ Failure to recognize kerion as immunological (NOT bacterial abscess) → Incorrect recommendation for incision/drainage

❌ Prescribing topical antifungals for tinea capitis → Inadequate therapy; oral antifungals mandatory

❌ Starting oral antifungals for onychomycosis without mycological confirmation → Risks unnecessary prolonged treatment; up to 50% of dystrophic nails are non-fungal

❌ Misdiagnosing tinea corporis as eczema → Missing the active scaly edge and central clearing

❌ Expecting Wood's lamp fluorescence for all tinea capitis → T. tonsurans (now most common) does NOT fluoresce

❌ Inadequate treatment duration → Stopping when clinically clear rather than continuing 1 week beyond resolution

---

13. Patient and Layperson Explanation

What are Tinea Infections?

Tinea infections, commonly called "ringworm" or "athlete's foot" depending on location, are fungal infections of the skin, hair, or nails. Despite the name "ringworm," no worm is involved—the name comes from the ring-shaped rash that often develops.

These infections are caused by fungi called dermatophytes that live on the dead outer layer of skin, hair, and nails. They are very common, affecting about 1 in 4 people at some point in their lives.

How Did I Get This?

You can catch tinea through:

• Direct contact with an infected person or animal (especially cats and dogs)
• Contaminated surfaces in warm, moist places like gym floors, swimming pool areas, or communal showers
• Sharing items like towels, combs, brushes, hats, or shoes with someone who has the infection

Factors that increase your risk:

• Warm, sweaty environments
• Wearing tight, non-breathable shoes
• Walking barefoot in public areas
• Close contact sports like wrestling
• Having diabetes or a weakened immune system

What Does It Look Like?

The appearance depends on where the infection is:

• On the body (ringworm): A ring-shaped red rash with raised, scaly edges and clearer skin in the middle
• On the feet (athlete's foot): Itchy, peeling skin between toes or scaly, dry skin on soles
• On the scalp: Patches of hair loss with scaling; sometimes a painful, swollen area (called a kerion)
• On the nails: Thickened, yellowed, crumbly nails
• In the groin (jock itch): Red, itchy rash in groin creases, extending to inner thighs

How Is It Treated?

Treatment depends on where the infection is:

Skin infections (body, feet, groin):

• Antifungal cream (like terbinafine or clotrimazole) applied twice daily for 1-4 weeks
• Available over-the-counter or by prescription
• Continue for 1 week after the rash clears to prevent it coming back

Scalp infections:

• Antifungal tablets (terbinafine or griseofulvin) for 4-8 weeks
• Creams don't work for scalp infections because they can't reach the hair follicles
• Antifungal shampoo helps reduce spread to others

Nail infections:

• Antifungal tablets for 6 weeks (fingernails) to 12 weeks (toenails)
• Nails grow slowly, so it takes many months to see full improvement
• Cure rates are 60-80%, lower than skin infections

Is It Contagious?

Yes, tinea is contagious. To prevent spreading:

• Don't share towels, clothing, combs, or brushes
• Wash your hands after touching the infected area
• Once treatment starts, risk of spreading drops significantly
• Children can usually return to school/nursery once treatment begins (check local policy)
• If you have pets with skin problems, take them to a vet

How Can I Prevent Getting It Again?

• Keep skin clean and dry, especially between toes
• Wear breathable shoes and cotton socks; change socks daily
• Wear flip-flops in communal showers and pool areas
• Don't walk barefoot in public places
• Avoid sharing personal items
• Treat any nail infections (they can cause skin to keep getting reinfected)
• If you have athlete's foot, treat it promptly to prevent spread to other areas

When Should I See a Doctor?

See a doctor if:

• The rash doesn't improve after 2 weeks of over-the-counter treatment
• You have scalp hair loss or a painful scalp lump (needs urgent prescription treatment)
• The infection is widespread
• You have diabetes or a weakened immune system
• Signs of bacterial infection develop (increasing pain, redness, warmth, fever)

Most tinea infections are straightforward to treat and clear up completely with appropriate antifungal therapy. The key is using the right treatment for the right amount of time!

---

14. References

1. Ely JW, Rosenfeld S, Seabury Stone M. Diagnosis and management of tinea infections. Am Fam Physician. 2014;90(10):702-710. PMID: 25403034

2. Weitzman I, Summerbell RC. The dermatophytes. Clin Microbiol Rev. 1995;8(2):240-259. doi:10.1128/CMR.8.2.240

3. Havlickova B, Czaika VA, Friedrich M. Epidemiological trends in skin mycoses worldwide. Mycoses. 2008;51 Suppl 4:2-15. doi:10.1111/j.1439-0507.2008.01606.x

4. Drake LA, Dinehart SM, Farmer ER, et al. Guidelines of care for superficial mycotic infections of the skin: tinea corporis, tinea cruris, tinea faciei, tinea manuum, and tinea pedis. J Am Acad Dermatol. 1996;34(2 Pt 1):282-286. doi:10.1016/s0190-9622(96)80135-8

5. Crawford F, Hollis S. Topical treatments for fungal infections of the skin and nails of the foot. Cochrane Database Syst Rev. 2007;(3):CD001434. doi:10.1002/14651858.CD001434.pub2

6. Petrikkos G, Skiada A, Lortholary O, Roilides E, Walsh TJ, Kontoyiannis DP. Epidemiology and clinical manifestations of mucormycosis. Clin Infect Dis. 2012;54 Suppl 1:S23-34. doi:10.1093/cid/cir866

7. Ilkit M, Durdu M. Tinea pedis: the etiology and global epidemiology of a common fungal infection. Crit Rev Microbiol. 2015;41(3):374-388. doi:10.3109/1040841X.2013.856853

8. Pontes ZB, Lima Ede O, Oliveira NM, dos Santos JP, Ramos AL. Onychomycosis in João Pessoa City, Brazil. Rev Argent Microbiol. 2013;45(2):95-99. PMID: 23876287

9. Fuller LC, Barton RC, Mohd Mustapa MF, et al. British Association of Dermatologists' guidelines for the management of tinea capitis 2014. Br J Dermatol. 2014;171(3):454-463. doi:10.1111/bjd.13196

10. Aly R. Ecology and epidemiology of dermatophyte infections. J Am Acad Dermatol. 1994;31(3 Pt 2):S21-25. doi:10.1016/s0190-9622(08)81259-1

11. Gupta AK, Drummond-Main C, Cooper EA, Brintnell W, Piraccini BM, Tosti A. Systematic review of nondermatophyte mold onychomycosis: diagnosis, clinical types, epidemiology, and treatment. J Am Acad Dermatol. 2012;66(3):494-502. doi:10.1016/j.jaad.2011.02.038

12. Romano C, Rubegni P, Ghilardi A, Fimiani M. A case of bullous tinea pedis with tinea manuum due to Trichophyton mentagrophytes. Mycoses. 2006;49(3):249-250. doi:10.1111/j.1439-0507.2006.01228.x

13. Rippon JW. The changing epidemiology and emerging patterns of dermatophyte species. Curr Top Med Mycol. 1985;1:208-234. doi:10.1007/978-1-4613-9547-8_8

14. Higgins EM, Fuller LC, Smith CH. Guidelines for the management of tinea capitis. Br J Dermatol. 2000;143(1):53-58. doi:10.1046/j.1365-2133.2000.03597.x

15. Chermette R, Ferreiro L, Guillot J. Dermatophytoses in animals. Mycopathologia. 2008;166(5-6):385-405. doi:10.1007/s11046-008-9102-7

16. Jousson O, Léchenne B, Bontems O, et al. Secreted subtilisin gene family in Trichophyton rubrum. Gene. 2004;339:79-88. doi:10.1016/j.gene.2004.06.024

17. Campos MR, Russo M, Gomes E, Almeida SR. Stimulation, inhibition and death of macrophages infected with Trichophyton rubrum. Microbes Infect. 2006;8(2):372-379. doi:10.1016/j.micinf.2005.07.006

18. Honig PJ, Smith L. Treatment of kerion and dermatophytoses in children. Pediatr Ann. 2007;36(1):60-65. doi:10.3928/0090-4481-20070101-11

19. Adams BB. Tinea corporis gladiatorum. J Am Acad Dermatol. 2002;47(2):286-290. doi:10.1067/mjd.2002.120790

20. Elewski BE. Onychomycosis: pathogenesis, diagnosis, and management. Clin Microbiol Rev. 1998;11(3):415-429. doi:10.1128/CMR.11.3.415

21. Gupta AK, Taborda P, Taborda V, et al. Epidemiology and prevalence of onychomycosis in HIV-positive individuals. Int J Dermatol. 2000;39(10):746-753. doi:10.1046/j.1365-4362.2000.00782.x

22. Ive FA, Marks R. Tinea incognito. Br Med J. 1968;3(5611):149-152. doi:10.1136/bmj.3.5611.149

23. Williams JV, Honig PJ, McGinley KJ, Leyden JJ. Semiquantitative study of tinea capitis and the asymptomatic carrier state in inner-city school children. Pediatrics. 1995;96(2 Pt 1):265-267. PMID: 7630682

24. Weinberg JM, Koestenblatt EK, Tutrone WD, Tishler HR, Najarian L. Comparison of diagnostic methods in the evaluation of onychomycosis. J Am Acad Dermatol. 2003;49(2):193-197. doi:10.1067/s0190-9622(03)00653-7

25. Brillowska-Dabrowska A, Saunte DM, Arendrup MC. Five-hour diagnosis of dermatophyte nail infections with specific detection of Trichophyton rubrum. J Clin Microbiol. 2007;45(4):1200-1204. doi:10.1128/JCM.02072-06

26. Gupta AK, Drummond-Main C. Meta-analysis of randomized, controlled trials comparing particular doses of griseofulvin and terbinafine for the treatment of tinea capitis. Pediatr Dermatol. 2013;30(1):1-6. doi:10.1111/j.1525-1470.2012.01866.x

27. Friedlander SF, Aly R, Krafchik B, et al. Terbinafine in the treatment of Trichophyton tinea capitis: a randomized, double-blind, parallel-group, duration-finding study. Pediatrics. 2002;109(4):602-607. doi:10.1542/peds.109.4.602

28. De Backer M, De Vroey C, Lesaffre E, Scheys I, De Keyser P. Twelve weeks of continuous oral therapy for toenail onychomycosis caused by dermatophytes: a double-blind comparative trial of terbinafine 250 mg/day versus itraconazole 200 mg/day. J Am Acad Dermatol. 1998;38(5 Pt 3):S57-63. doi:10.1016/s0190-9622(98)70486-4

29. Gupta AK, Dlova N, Taborda P, et al. Once weekly fluconazole is effective in children in the treatment of tinea capitis: a prospective, multicentre study. Br J Dermatol. 2000;142(5):965-968. doi:10.1046/j.1365-2133.2000.03476.x

30. Fuller LC, Barton RC, Mohd Mustapa MF, et al. British Association of Dermatologists' guidelines for the management of tinea capitis 2014. Br J Dermatol. 2014;171(3):454-463. doi:10.1111/bjd.13196

31. NICE Clinical Knowledge Summary. Fungal skin infection - body and groin. Accessed December 2024. https://cks.nice.org.uk/topics/fungal-skin-infection-body-groin/

32. Gupta AK, Daigle D, Foley KA. The prevalence of culture-confirmed toenail onychomycosis in at-risk patient populations. J Eur Acad Dermatol Venereol. 2015;29(6):1039-1044. doi:10.1111/jdv.12873

---

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances and evolving evidence. Always consult appropriate specialists and current guidelines for definitive management recommendations.