Seborrhoeic dermatitis and cradle cap — formative SAQs

SAQ 1 (10 marks) — The six-week-old with the greasy yellow scalp scale

Stem: A six-week-old boy is brought to the general practice with a yellow, greasy, crusty layer over his scalp for two weeks. He is feeding well, gaining weight, and smiling, and he is not scratching or irritable. The scale sits over the vertex and the anterior fontanelle, with a little behind the ears and in the eyebrows, and there is a faint salmon-pink patch in the napkin folds. The parents are anxious that he has an infection and have borrowed a potent steroid cream. Outline your assessment, your management, and your discharge counselling. [1] [5]

Model answer

Assessment and diagnosis (3 marks). This is the classic presentation of the infantile seborrhoeic dermatitis, or the cradle cap. The decisive features are the three signatures: the greasy yellow scale rather than the dry eczematous scale, the involvement of the napkin folds that the atopic dermatitis characteristically spares, and the absent pruritus — the infant is well and settled and does not scratch. The diagnosis is clinical, no swab or scraping or blood test is required, and the well appearance and the normal growth argue against the red-flag deterioration. The borrowed potent steroid is stopped at once. [5]

Management — the gentle scalp care (5 marks). The first and the central element is the reassurance: the condition is common, benign, and self-limiting, it is neither an infection nor a hygiene problem nor a contagion, and it clears by six to twelve months. The scale is softened with an emollient or a vegetable oil such as the olive or the almond oil, left for fifteen minutes to a few hours, loosened with the gentle brushing, and washed with the mild baby shampoo. The picking and the harsh scrubbing are avoided. The Victoire 2019 Cochrane review found the very low-certainty evidence for the active treatments and the favourable prognosis regardless of the intervention, and it noted that no trial had tested the mineral oil, the salicylic acid, or the antifungal. The ketoconazole two per cent shampoo and the hydrocortisone one per cent are reserved for the refractory or the extensive case, not the classic one. [1] [6]

Discharge counselling (2 marks). The family is counselled that the cradle cap is benign, that the sebum and the Malassezia yeast rather than the hygiene drive it, and that it clears by six to twelve months. They are shown the gentle scalp-care technique and told to avoid the picking and the potent steroid. The safety-net advice is to return if the eruption generalises into the erythroderma, if the infant becomes unwell or fails to thrive, or if the disease persists or worsens beyond infancy. No follow-up is needed in the classic case. [5] [1]

SAQ 2 (10 marks) — The generalised erythroderma and the Leiner disease red flag

Stem: A three-month-old infant presents with the generalised redness and the desquamation that has progressed over a week, alongside the profuse diarrhoea and the poor weight gain. Separately, contrast this with the eight-month-old whose cradle cap has not cleared and who now has the patchy hair loss and the occipital lymphadenopathy. Discuss the Leiner disease diagnosis and the management, the immunodeficiency workup of the refractory disease, and the principle that governs the tinea capitis differential of the scaly scalp. [3] [5]

Model answer

Leiner disease — the diagnosis and the management (4 marks). The generalised erythroderma and the desquamation, with the diarrhoea and the failure to thrive, is the Leiner disease (erythroderma desquamativum), and this is a life-threatening emergency. The clinical tetrad is the generalised erythroderma, the persistent gastrointestinal disturbance with the diarrhoea and the malabsorption and the wasting, the superimposed bacterial or candidal infection, and the marked wasting. The defective opsonisation and the complement C3 deficiency or the C5 dysfunction underlie the familial form, on the Sanghvi 2021 review. The management is the admission, the fluid and the nutrition support, the antibiotics for the infection, and the fresh-frozen plasma to correct the defective opsonisation. The disease is distinguished from the Omenn syndrome and the other infantile erythrodermas. [3]

The refractory disease and the immunodeficiency workup (3 marks). The cradle cap that does not clear by six to twelve months, and the disease that persists or worsens beyond infancy in the child with the failure to thrive, is the trigger for the immunodeficiency workup. The severe combined immunodeficiency, the HIV, and the Langerhans cell histiocytosis present with the refractory or the severe seborrhoeic-like eruption, and the blood count, the immunoglobulins, the lymphocyte subsets, the HIV test, and the skin biopsy frame the workup. The benign cradle cap clears by six to twelve months, and the deviation from this course escalates the assessment. [3] [5]

The tinea capitis differential and the principle of the scaly scalp (3 marks). The eight-month-old with the cradle cap that has not cleared, and with the patchy hair loss and the occipital lymphadenopathy, has the tinea capitis, not the cradle cap. The cradle cap does not cause the hair loss and does not cause the lymphadenopathy, and the presence of either shifts the diagnosis. The potassium hydroxide preparation and the fungal culture confirm the dermatophyte, and the management is the oral antifungal, not the shampoo. The principle is that the scaly infant scalp is the cradle cap until the hair loss, the lymphadenopathy, the pruritus, or the failure to thrive argue otherwise — and the pattern that does not fit the cradle cap is the trigger for the reconsideration and the workup. [5]