Pityriasis rubra pilaris: a new proposed classification

Clinical features of pityriasis rubra pilaris (PRP) were classified into four types based on a study of 168 cases. All patients, except one case of type IV, and 12 cases of type II, have salmon-coloured or erythematous thick plaques on the palms and soles, which extended beyond the dorsopalmar and plantar junctions. Twenty-one children and 11 adults presenting with such plaques were classified as type I PRP. Fifty-nine children and 27 adults presenting with circumscribed scaly erythematous patches on the elbows and knees were classified as type II. Twenty children and 16 adults with similar patches involving large areas of the trunk which were not generalized were classified as type III. Four children and 10 adults with exfoliative erythroderma associated with diffuse follicular plugging were classified as type IV. The diagnosis was confirmed by histopathology which showed follicular plugging and focal parakeratosis. However, this was not seen in type I. This new clinical classification facilitates recognition of this type of PRP despite the absence of follicular plugging. Two children, initially classified as type I, showed gradual progression to type II on follow-up, with two adults progressing to type III, and 1 adult to type IV. Similarly, two adults classified as type II, progressed to type III, and 1 adult into type IV. Associated findings were an adult of type II who developed localized pustular psoriasis and another adult who developed ovarian adenocarcinoma.