Cutaneous sarcoidosis: the "great imitator": etiopathogenesis, morphology, differential diagnosis, and clinical management.

Sarcoidosis is a multisystem disease that can involve almost any organ system. The underlying cause of the disease remains unknown. Immunopathologically and histologically, cutaneous sarcoidosis is characterized by a macrophage/T helper-1 cell-mediated, non-caseating, granulomatous inflammation process. An imbalance between proinflammatory and anti-inflammatory cytokines plays an important role in the development of cutaneous granulomas. Recognition of cutaneous sarcoidosis lesions is very important because they provide a visible clue to the diagnosis and are an easily accessible source of tissue for histologic examination. Because skin lesions of patients with the disease can exhibit many different morphologies, cutaneous sarcoidosis is known as one of the "great imitators" in dermatology. Specific manifestations can include patches (sometimes hypopigmented), papules, scar sarcoidosis, ulcers, ichthyosis, and alopecia. The treatment of cutaneous sarcoidosis is often frustrating because some of the skin lesions may be refractory to treatment or may recur following successful treatment. Systemic and topical corticosteroids are the most effective treatments for cutaneous sarcoidosis. This article focuses on the dermatologic aspects of sarcoidosis and includes a review of the most recent literature, which includes new data on the diagnosis, differential diagnosis, pathogenesis, and treatment of the disease.