Pityriasis rubra pilaris: Clinicopathological study of 32 cases from Lebanon

Abstract

Background: Pityriasis rubra pilaris (PRP) is an uncommon papulosquamous disorder of unknown etiology. Studies on this condition from our region are lacking. Methods: To describe the clinical and histopathological findings as well as response to treatment of all patients diagnosed with PRP at the American University of Beirut Medical Center between 1995 and 2010 and compare our findings with those published in the literature. Results: Pityriasis rubra pilaris was diagnosed in 32 patients (16 males, 16 females). Age of onset ranged between 2.5 and 70 years. The majority of patients (n = 15) were classified as type I (47%) followed by type III (n = 9, 28%) and type IV (n = 6, 19%). Based on treatment responses, retinoids appear to be very effective in our population as all patients treated with isotretinoin or acitretin had excellent response. In addition to checkerboard alternating orthokeratosis/parakeratosis, which was observed in 31 cases, interesting features, including the presence of follicular plugging in all 21 cases in which follicles were available for examination, eosinophils in 12 cases, and focal acantholysis in three cases were observed. Conclusions: Features of patients with PRP in our study are generally comparable to those published in the literature, with minor differences. Microscopically follicular plugging, in addition to checkerboard alternating orthokeratosis/parakeratosis, may serve as clues to PRP diagnosis. The presence of eosinophils and focal acantholysis, observed in a few cases, should not exclude PRP diagnosis. © 2013 The International Society of Dermatology.