Circumscribed juvenile pityriasis rubra pilaris

Pityriasis rubra pilaris (PRP) is an uncommon papulosquamous inflammatory dermatosis of unclear aetiology. Its most remarkable clinical findings are palmoplantar hyperkeratosis, orange-red scaling plaques and hyperkeratotic follicular papules. Its extension may vary from localised subtypes to generalised skin involvement with well-demarcated areas of spared skin ("islands of sparing") to erythroderma. Griffiths' classification is used to distinguish PRP in five clinical subtypes. Diagnosis is based on clinical and histopathological findings. The main differential diagnosis in a patient with circumscribed juvenile PRP (type IV) is psoriasis although keratosis pilaris, lichen spinulosus and follicular ichthyosis must also be ruled out. Treatment of pityriasis rubra pilaris remains a controversial topic due to the lack of large-scale clinical randomised trials and its unpredictable spontaneous resolution.