Granulomatous Mastitis with Erythema Nodosum: A Case Report and Systematic Review

A healthy G5P3 34-year-old Hispanic patient with a new diagnosis of granulomatous mastitis of the right breast was referred to the dermatology clinic for painful skin lesions that had enlarged over the week prior and arthralgia in her knees and elbows. Examination revealed multiple tender, erythematous subcutaneous nodules scattered over the extensor surfaces of bilateral upper and lower extremities. Histology from the right forearm exhibited a mixed septal and lobular panniculitis with acute neutrophilic inflammation with granulomatous changes, consistent with erythema nodosum. The patient experienced significant improvement with prednisone taper, but flared on discontinuation; methotrexate was started with stabilization of her disease. Although once considered a rare association, GM associated with EN is increasingly recognized, and since 1987, a total of 28 reports have detailed 59 cases (including the present case). Here, we provide a comprehensive review of all 58 reported cases of this association, including ours. We found a preponderance of cases occurred in females of Turkish ancestry around the fourth decade of life in the peripartum period. Arthralgia is the most common additional symptom. The majority of cases responded to treatment with oral corticosteroids, but some required the addition of other immunosuppressants and/or definitive surgical excision.