The many faces of necrobiosis lipoidica: a report of three cases with histologic variations

Necrobiosis lipoidica (NL) is a granulomatous disease with unknown etiology and pathogenesis. Clinically, it is characterized by yellow-brown atrophic plaques with inflammatory rims on shins. Histologically, it shows diffused palisade and interstitial granulomatous dermatitis with focal connective tissue degeneration (necrobiosis). We described three non-diabetic NL cases with unusual histologic features. All patients presented erythematous to brownish plaque(s) on the shin(s). In Case 1, in addition to the characteristics of NL, the biopsy showed dense perineural infiltration, which may explain the pathogenesis of the anesthesia of NL lesions. In Case 2, well-formed tuberculoid granulomas were of special interest. In Case 3, there was conspicuous lobular panniculitis. These histologic features present difficulties in the diagnosis and represent the broad spectrum of NL lesions, histologically.