Approach to rash in infants and children — formative SAQs

SAQ 1 (10 marks, 15 minutes)

Stem: A 3-year-old is brought to the emergency department with fever, irritability and a rash that has spread over the last four hours. On examination the child is drowsy, tachycardic, and has several lesions on the limbs that do not fade under glass-slide pressure. Outline your structured approach, immediate management, and the reasoning that underpins it. [7]

Model answer (marker scaffold)

Immediate recognition and threat assessment (3 marks):

• State that an unwell, febrile child with a non-blanching (purpuric) rash is presumed to have invasive bacterial sepsis, classically meningococcaemia, until proven otherwise.
• Apply a morphology-first, distribution-aware approach: morphology is purpura (extravasated blood); distribution is spreading and systemic; the unwell child makes this an emergency regardless of the named diagnosis.
• State the principle: resuscitate and treat the threat first; do not delay antibiotics for investigations or for the rash to "look typical". [7]

Immediate management (4 marks):

• ABCDE: oxygen, airway and breathing support; establish intravenous or intraosseous access.
• Take blood cultures and a meningococcal PCR, but give a parenteral third-generation cephalosporin (e.g. ceftriaxone or cefotaxime) immediately per local paediatric sepsis protocol - exact dose by weight and age.
• Manage shock with fluid boluses; reassess after every intervention; involve senior paediatric staff and retrieval early.
• Lumbar puncture only if clinically safe and indicated, and never before antibiotics in a shocked child. [7]

Reasoning and safety-net (3 marks):

• Explain why blanching is the key bedside discriminator: purpura does not blanch because blood is outside the vessel.
• Name the diagnostic trap of early meningococcaemia being nonspecific before purpura evolves.
• State disposition: admit to a paediatric centre with PICU involvement as required; safety-net the family and notify public health once the diagnosis is confirmed. [7]

SAQ 2 (10 marks, 15 minutes)

Stem: A 6-year-old presents with widespread tender erythema, flaccid superficial blisters and peeling, with skin shearing under tangential pressure. The oral mucosa is spared. Contrast this presentation with Stevens-Johnson syndrome / toxic epidermal necrolysis, justify the diagnosis, and outline management principles. [9] [10]

Model answer (marker scaffold)

Diagnosis with justification (4 marks):

• Diagnose staphylococcal scalded skin syndrome: superficial tender erythema with flaccid blisters, superficial peeling, a positive Nikolsky sign, flexural accentuation, and sparing of the mucosa.
• State the mechanism: a staphylococcal exfoliative toxin cleaves desmoglein-1 in the superficial epidermis, producing a subcorneal split.
• Contrast with SJS/TEN: full-thickness (basal-layer) epidermal necrosis, drug- or infection-triggered, and prominent mucosal involvement; both can have a positive Nikolsky sign, so the cleavage plane and mucosal pattern decide it. [10]

Why the distinction matters (2 marks):

• The cleavage plane predicts severity and complications: SSSS is superficial and heals without scarring but can cause fluid and temperature loss; SJS/TEN is full-thickness, risks fluid and electrolyte loss, sepsis and ocular adhesion complications, and carries higher mortality.
• This justifies the difference in escalation and the involvement of ophthalmology and burns for SJS/TEN. [9]

Management principles (4 marks):

• Supportive: fluid, electrolyte and temperature support; aseptic skin and wound care; analgesia; monitor for secondary infection.
• An anti-staphylococcal antibiotic; involve dermatology, and burns or PICU for extensive disease.
• For SJS/TEN specifically: stop the suspected culprit drug immediately, involve ophthalmology to prevent adhesions and corneal damage, and arrange burns or PICU care.
• Safety-net and arrange follow-up; address any source focus of staphylococcal infection. [10]