Granulomatous Mastitis with Erythema Nodosum and Erysipelas-like Lesions: Expanding the GMENA Syndrome.

Granulomatous mastitis (GM) is a rare, benign inflammatory breast condition that occasionally presents with systemic features such as erythema nodosum (EN) and arthritis, collectively termed GMENA syndrome. We report a unique case of a 32-year-old woman with GM, EN, and an erysipelas-like skin lesion (ELL) in the absence of arthritis. Despite antibiotic therapy, her condition deteriorated with persistent fever and elevated inflammatory markers. Cultures remained sterile, while biopsies confirmed idiopathic GM and non-infectious perivascular dermal inflammation. Immune work-up revealed antiphospholipid antibodies, suggesting an underlying immune-mediated process. Initiation of systemic corticosteroids led to rapid resolution of symptoms and normalization of inflammatory markers. This case highlights a previously unreported triad-GM with EN and ELL-and suggests that GM may trigger immune-driven microvascular inflammation beyond classical GMENA. Clinicians should be alert to sterile, infection-mimicking skin manifestations in GM, particularly when antibiotic treatment fails. Early recognition and timely immunosuppression can be critical for favourable outcomes and may prevent unnecessary antibiotic use or invasive procedures. The co-existence of antiphospholipid antibodies raises questions regarding their role in the pathogenesis of systemic features in GM, warranting further investigation.