A Pediatric Case with Erythematous Plaques and Palmoplantar Keratoderma

Papulosquamous disorders in children often display distinctive features, clinically and histopathologically, that hold important clues to diagnosis. Response to therapy might differ from that in adults. Herein we describe an otherwise healthy 4-year-old boy, referred to our clinic for rash on the head, trunk, palms and soles starting around one month prior to consultation. Pruritus was mild and did not interfere with daily routines. However, the rash tended to spread and was unresponsive to topical corticosteroids and moisturizers. Medical history was not contributory. Physical examination was unremarkable except for coalescing erythematous papules encircling islands of normal skin on the head and trunk, and thickened palms and soles. Histopathology showed psoriasiform hyperplasia, broad and elongated rete ridges, and the characteristic alternating parakeratosis. Collection of neutrophils in the stratum corneum and granulosum was noticeably absent. Other laboratory results were within normal limits. Despite the lack of tell-tale salmon color in the patient’s dark-skin type, his other clinical and histopathological features favored the diagnosis of pityriasis rubra pilaris. Treatment with methotrexate was commenced with a dose of 5 mg weekly. However, after approximately a year the result was marginal, so that we switched to phototherapy. Based on a small number of successful reports, we decided to treat with narrow-band ultraviolet B phototherapy. The initial dose was 200 mJ/cm2 twice weekly, with 20% increment up to 1.125 mJ/cm2 over 6 weeks when significant improvement was observed. The dose was then tapered down; currently the patient still received 390 mJ/cm2 fortnightly with his condition being stable.