Nappy dermatitis — formative SAQs

SAQ 1 (10 marks) — The nine-month-old with the spreading nappy rash after antibiotics

Stem: A nine-month-old boy is brought to the general practitioner with a five-day history of a red, sore rash in the nappy area. The rash began on the buttocks and has spread into the groin folds in the last two days, with small red bumps appearing at the edge. He completed a course of oral amoxicillin for an ear infection ten days ago. On examination, the buttocks, the genitalia, and the lower abdomen show a confluent bright erythema, the inguinal folds are involved, and there are five small red papules and two tiny pustules scattered on the upper thighs beyond the main margin. He is afebrile and well. Outline your assessment, your diagnosis, and your management plan. [2] [4]

Model answer

Assessment and diagnosis (3 marks). This is a candidal nappy dermatitis, almost certainly secondary to the recent amoxicillin course, superimposed on an irritant base. The decisive features are the involvement of the inguinal folds — which the irritant subtype characteristically spares — and the satellite papules and pustules scattered beyond the main margin, which are the pathognomonic feature of the candidal subtype. The recent antibiotic course is the precipitant, because it disrupts the normal flora and allows the Candida overgrowth. The child is well and afebrile, which argues against the secondary bacterial infection. [1] [4]

Management — the general skin care and the barrier (3 marks). The management is the general skin care, the barrier preparation, and the antifungal. The nappy is changed every two to three hours and after every stool, the super-absorbent disposable nappy is used, and the skin is cleansed with warm water and a soft cloth — not the alcohol or the fragranced wipe — and patted dry. The zinc oxide paste at fifteen to forty percent or the petrolatum is applied generously at every nappy change, and the old layer is gently wiped rather than scrubbed off, so the skin is not traumatised. [3]

Management — the antifungal (3 marks). The candidal subtype warrants the topical antifungal, added to the barrier. The clotrimazole 1 percent cream or the miconazole 2 percent cream is applied twice daily for ten to fourteen days to the affected skin, before the barrier layer, so the antifungal reaches the skin and the barrier protects it. The hydrocortisone 1 percent cream, once or twice daily for three to five days, is added if the inflammation is intense, applied sparingly to the inflamed skin. The potent steroids are avoided in the nappy area because the occlusion increases the absorption and the risk of the skin atrophy. [4] [5]

Counselling and follow-up (1 mark). The family is counselled that the Candida is the consequence of the antibiotic disruption of the normal flora, not a sign of a serious underlying condition. The improvement is expected within three to five days. The rash that does not respond in seven days demands the broader differential — the seborrhoeic, the atopic, the allergic, the psoriatic, the zinc deficiency, and the Langerhans cell histiocytosis — and the return for review. [2]

SAQ 2 (10 marks) — The persistent nappy rash and the broader differential

Stem: A fourteen-month-old girl is referred to the paediatric clinic with a nappy rash that has persisted for four weeks despite the zinc oxide barrier and the clotrimazole cream prescribed by the general practitioner. The rash involves the inguinal folds, the perianal area, and the perioral skin, and there is a chronic, intermittent diarrhoea. The growth chart shows the weight crossing two centile lines downward. Describe your approach to the persistent nappy rash, the differential diagnosis, and the investigations. [6] [7]

Model answer

The principle of the persistent rash (3 marks). A nappy rash that does not respond to the good barrier measures and the appropriate antifungal within seven days is not a treatment failure. It is a diagnostic reconsideration. The rash that has persisted for four weeks despite the zinc oxide barrier and the clotrimazole cream, particularly with the perioral extension and the chronic diarrhoea, demands the broader differential — the seborrhoeic dermatitis, the atopic dermatitis, the allergic contact dermatitis, the psoriasis, the zinc deficiency of the acrodermatitis enteropathica, and the Langerhans cell histiocytosis. The weight loss crossing the centile lines raises the concern for the underlying systemic condition. [6]

The differential diagnosis (4 marks). The distribution is the key to the differential. The involvement of the perioral skin alongside the nappy-area and the perianal rash, the chronic diarrhoea, and the failure to thrive point to the zinc deficiency, the acrodermatitis enteropathica. This is the autosomal recessive disorder of the zinc absorption, and it presents with the periorificial dermatitis — around the mouth, the anus, and the genitalia — the chronic diarrhoea, and the alopecia. The seborrhoeic dermatitis presents with the greasy scales in the folds and the scalp, but it does not cause the failure to thrive. The psoriasis presents with the well-defined plaques, and the Langerhans cell histiocytosis presents with the purpuric, crusted papules in the seborrhoeic distribution. The allergic contact dermatitis tracks the allergen contact and does not extend to the perioral skin. [6] [7]

The investigations (3 marks). The serum zinc level is the first test, and the low level confirms the acrodermatitis enteropathica. The alkaline phosphatase, a zinc-dependent enzyme, is also low and supports the diagnosis. The skin biopsy, with the characteristic changes, is the confirmatory test if the zinc level is equivocal. The dermatology referral and the paediatric gastroenterology referral are made for the combined management of the skin and the nutrition. The oral zinc supplementation, at two to three milligrams per kilogram per day of the elemental zinc, is the treatment, and the response is rapid, with the skin clearing within days to weeks. The child-protection awareness is maintained when the failure to thrive and the persistent rash raise the concern for the neglect, and the social-paediatrics team is involved alongside the medical workup. [7]