Atypical necrobiosis lipoidica presenting outside the pretibial region

Abstract

Necrobiosis lipoidica (NL) is a rare chronic granulomatous dermatosis classically associated with diabetes mellitus and typically affecting the pretibial surfaces. Extrapretibial involvement, particularly on the forearm, is uncommon and may create diagnostic difficulty because lesions outside the lower legs can lack the classic clinical distribution of NL. We report a 24-year-old woman with poorly controlled type 1 diabetes mellitus who presented with a slowly enlarging, occasionally pruritic plaque on the left dorsal forearm for approximately 10 years. Skin examination revealed a solitary well-defined atrophic shiny telangiectatic plaque with a central yellow hue and peripheral erythema over the extensor surface of the left forearm. Histopathological examination demonstrated necrobiotic granuloma with foci of dermal necrobiosis surrounded by lymphohistiocytic infiltrate and scattered plasma cells, confirming the diagnosis of necrobiosis lipoidica. The patient was treated with intralesional corticosteroid injections, with further therapy planned according to clinical response.Necrobiosis lipoidica can rarely present at extratibial sites, including the dorsal forearm. Recognition of this atypical presentation is important, as clinical diagnosis may be delayed when lesions occur outside the classic pretibial location. Skin biopsy remains essential for confirming the diagnosis and guiding appropriate management.