Abstract

A 58-year-old female presented with a one-year history of intermittent rash on her trunk and extremities, with examination notable for erythematous firm papules coalescing into plaques with post inflammatory hyperpigmentation. She denied any relevant medication history, chronic illnesses, or systemic symptoms. Histopathology revealed areas of well-formed sarcoidal granulomas with a lymphocytic cuff on the first two specimens. However, the third specimen also revealed a prominent interstitial granulomatous infiltrate extending into the deep dermis. GMS, AFB and Fite stains were negative for organisms. Colloidal iron stain highlighted increased dermal mucin in association with the interstitial infiltrate. Overall, the histologic findings were consistent with a granulomatous dermatitis. Given that both sarcoidal and interstitial granulomas were present, a diagnosis of the sarcoidal form of granuloma annulare (GA) was favored, especially given further pulmonary workup was negative for definitive evidence of sarcoidosis. This case highlights a lesser-known form of granuloma annulare, as typically most cases of GA present with palisaded or interstitial inflammation. The patient was started on oral minocycline, with significant improvement in cutaneous findings. This case demonstrates that the sarcoidal form of granuloma annulare may be misdiagnosed as sarcoidosis if only the well-formed granulomas are present. The presence of interstitial granulomas, in addition to lack of systemic symptoms, are helpful clues to a diagnosis of the sarcoidal form of granuloma annulare.