Cutaneous sarcoidosis masquerading as psoriatic plaques

Abstract

Sarcoidosis is a multisystem disease characterized by non-caseating granulomas present in the involved organ systems. The disease is believed to result from an interaction among genetic factors, antigens, and the immune response. Environmental exposures and infectious agents have been implicated as potential causes [1]. Cutaneous sarcoidosis presents clinically in many forms and the lesions are classified as either specific or non-specific. Non-specific lesions show a nondescript inflammatory process [2] whereas specific lesions display typical, non-caseating granulomas. There are many different forms of specific lesions with some being more common than others. Psoriasiform lesions are uncommon [1]. The literature suggests that as few as 0.9% of patients display this type of cutaneous sarcoidosis [3]. Some of these patients present solely with cutaneous sarcoidosis, but others have systemic involvement with pulmonary involvement being the most common concomitant presentation [4-8]. Plaques appear as round or oval, brownish, red infiltrated lesions [9], frequently involving the extensor surface of the extremities, face, scalp, back, and buttocks [9, 10]. Multiple configurations, including discrete, confluent, annular, and polycyclic, have been reported [5 11]. Despite the clinical resemblance to psoriasis, on histological examination, only non-caseating granulomas are seen in the dermis. In rare cases both psoriasiform sarcoidosis and psoriasis were present [4].