Histoid leprosy: review of the literature

Leprosy is a chronic granulomatous inflammation primarily of the peripheral nervous system, skin, and reticuloendothelial system caused by Mycobacterium leprae. It presents clinically as an erythematous or hypopigmented anesthetic patch and a thickened and/or tender cutaneous nerve trunk. Leprosy is also called Hansen disease. Leprosy is a great imitator of other skin diseases, and it can present with different morphological lesions, which is why an expert eye is needed to diagnose it. One of the important clinical presentations of leprosy is histoid leprosy, which is very difficult to diagnose due to different clinical and histopathological findings that mimic, e.g., a fibromatous disorder. Histoid leprosy is a very rare clinicopathological variant of leprosy. It is clinically characterized by skin-colored, soft, succulent nodules, and plaques on apparently normal skin and histologically by a dense bundle of histiocytes arranged in storiform. Though histoid leprosy is a very rare type of leprosy, the higher load of lepra bacilli in these cases makes it a concern as a reservoir for leprosy.