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Abstract

A 74-year-old woman with chronic obstructive pulmonary disease and diabetes mellitus presented to her dermatologist for an asymptomatic, slowly-expanding, brown patch with underlying induration on her left lower leg that had been present for years. A biopsy captured a granulomatous process spanning the dermis and extending into the subcutis. Nodular collections of epithelioid histiocytes, some multinucleated, were surrounded by lymphocytes and plasma cells. There were also palisaded histiocytes associated with sclerotic collagen. A PAS-D and Fite stain did not reveal fungi or mycobacteria, respectively. These findings, which contained features of necrobiosis lipoidica, were favored to represent sarcoidosis. The patient returned four years later with the untreated original lesion having enlarged into a yellowish-brown plaque and new, similar lesions on her left knee. A biopsy of one of the new lesions captured findings resembling the original biopsy; however, this new granulomatous inflammation in the superficial and deep dermis consisted of small aggregates of macrophages, multinucleated histiocytes, and plasma cells–as opposed to well-formed granulomas–palisaded around horizontally oriented, non-necrobiotic, focally sclerotic collagen. An Alcian blue (pH 2.5) stain did not reveal dermal mucin. These findings were favored to represent necrobiosis lipoidica but could not exclude sarcoidosis as a sole or concurrent diagnosis. This case highlights the clinical and histologic overlap between necrobiosis lipoidica and sarcoidosis; there have been reports of a sarcoidal histologic type of necrobiosis lipoidica, necrobiosis lipoidica with sarcoidal features on histology, and concurrent necrobiosis lipoidica and sarcoidosis in patients both with and without diabetes.