A 23-year-old woman with Down syndrome presented erythematous keratotic plaques with whitish scales on the elbows, forearm, knee and leg. Histopathological findings revealed acanthosis with broad and short rete ridges, alternating orthokeratosis and parakeratosis oriented in both vertical and horizontal directions, and dermal superficial perivascular lymphocytic infiltration, compatible with pityriasis rubra pilaris.