A 2-year-old boy born to consanguineous parents presented with skin lesions over the body and scalp since six months of age. On examination he had multiple pinkish plaques with sharp borders over the chest, abdomen, back and upper arm with areas of normal skin in between the lesions (Fig. 1). His palms and soles were hyperkeratotic (Fig. 2). His hair, teeth, nails and oral mucous membrane were normal. Skin biopsy showed hyperkeratosis, parakeratosis, acanthosis and scattered mononuclear cell inflammatory infiltrates in the upper dermis. A diagnosis of pityriasis rubra pilaris (PRP) was made.

Fig.1. Multiple pinkish plaques over the chest, abdomen and upper arm with areas of normal skin in between lesions.	Fig.2. Hyperkeratosis of palms.

PRP is an uncommon dermatosis characterized by diffuse scaling and erythematous papules coalescing into plaques over the head, neck and trunk. The lesions have sharp borders and islands of normal skin within them. There is gross hyperkeratosis with painful fissures of the palms and soles. Hyperkeratotic plaques may also occur on knees and elbows. Pruritus is usually absent. Differential diagnosis includes ichthyosis, seborrheic dermatitis (for scalp lesions), keratoderma of palms and soles, and psoriasis (especially when dystrophic nail changes are seen). The cause of PRP is unknown. The genetic form with autosomal dominant transmission may account for some cases in childhood but most cases appear to be sporadic. The course of PRP is usually prolonged interspersed by remission and exacerbations. Some patients respond to topical keratolytic therapy and others may require oral retinoids.