Multicentric reticulohistiocytosis-mimicking dermatomyositis. Case report and review of the literature.

Multicentric reticulohistiocytosis is a rare disorder of unknown etiology, characterized by skin and mucosal papulonodular eruptions and destructive polyarthritis. Histopathological study of these lesions shows a nodular infiltrate composed of histiocytes and multinucleated giant cells, with an eosinophilic, granular, 'ground-glass' cytoplasm. We report a case of multicentric reticulohistiocytosis with skin lesions mimicking dermatomyositis and we also review previously reported cases describing such a clinical situation. Our case further emphasizes that multicentric reticulohistiocytosis can mimic clinical features of dermatomyositis. A macular or patch-like erythema in a photodistributed fashion, in addition to other clinical manifestations, can be mistaken for dermatomyositis. However, skin biopsies from these areas may early differentiate both conditions with different treatment options and morbidity.