A case of idiopathic granulomatous mastitis associated with erythema nodosum

What is known about this subject in regard to women and their families? Granulomatous mastitis (GM) is an uncommon and often misdiagnosed inflammatory breast condition. What is new from this article as messages for women and their families? There is growing recognition that GM can be associated with erythema nodosum, and the 2 diagnoses together may indicate a worse prognosis. Dear Editors, A healthy 22-year-old female presented to the hospital for recurrent breast abscesses along with new tender lesions on the bilateral shins. The patient had been evaluated 10 months prior for left breast erythema and induration, which was diagnosed as nonlactational mastitis. She was prescribed antibiotics, and her symptoms resolved over 2 weeks. Six months later, her symptoms reoccurred. Breast ultrasound revealed 2 masses (1.9 cm and 2.3 cm) with no clear fluid collection. Biopsy showed normal breast parenchyma with neutrophils and hemorrhage. Tissue cultures grew 1+ Gram-positive bacilli with no speciation. She was again started on empiric antibiotics. Ultrasound 2 and 4 weeks later revealed an evolving fluid collection, measuring up to 7.5 cm. Fluid cultures were negative. One week later, the patient presented with new painful red nodules on bilateral shins accompanied by fevers and joint pains. Upon admission, she was hemodynamically stable but febrile to 38.2 °C. Laboratory studies were notable for an elevated white blood cell count of 17.5 cells/μL and elevated inflammatory markers (erythrocyte sedimentation rate, 54; C-reactive protein, 8.6). Blood cultures were negative. Repeat breast ultrasound showed recurrence of her complex fluid collection, and magnetic resonance imaging revealed multiloculated fluid collections in the left breast with associated inflammation and reactive axillary lymphadenopathy, favoring a granulomatous process versus abscess. Fluid cultures were again negative. While inpatient, dermatology was consulted for the tender leg lesions. Physical exam was notable for multiple erythematous indurated tender nodules on the anterior low legs (Fig. 1). Punch biopsy revealed mixed dermal and septal inflammation, consistent with erythema nodosum (EN). Chest X-ray and quant gold were unremarkable.Fig. 1.: Multiple tender, erythematous, and indurated nodules on the anterior low legs.After evaluation by dermatology, breast surgery, and rheumatology, the patient was diagnosed with idiopathic granulomatous mastitis (IGM) accompanied by EN. IGM is a rare inflammatory breast condition characterized by the formation of granulomas within the breast tissue. The condition typically affects women of reproductive age and presents heterogeneously nut typically with breast pain, swelling, erythema, and a palpable mass.1 Imaging studies, such as mammography or ultrasound, may aid in diagnosis, often showing an irregularly shaped hypoechoic masses.1,2 However, radiologic findings can vary, thus definitive diagnosis often requires exclusion of other entities and confirmation with histopathologic findings on biopsy. Classic histologic features include nonnecrotizing granulomas and multinucleated giant cells, although organized sterile microabscesses with neutrophilic infiltrates and no obvious granulomas are also described, as seen in our patient.1 Treatment options for IGM include doxycycline, corticosteroids, methotrexate, azathioprine, and surgical intervention in more severe cases.3,4 Upon diagnosis, this patient was started on prednisone, which led to resolution of her fevers, EN, and marked improvement of her breast lesions. EN is typically characterized by painful, red nodules that typically appear on the shins but can also affect other parts of the body. It is considered a hypersensitivity reaction, and the underlying cause can vary. Common triggers include infections (such as streptococcal or mycobacterial infections), medications, autoimmune diseases, and inflammatory bowel disease. There is growing recognition of IGM associated with EN in the literature and evidence that IGM accompanied by EN may indicate a worse prognosis, with 2.3 times greater risk reoccurrence of IGM when associated with EN compared with those who lack EN.4,5 Indeed, our patient developed reoccurrence of her left breast collection 10 months later. Conflicts of interest None. Funding None. Study approval N/A Author contributions NU and SB: Participated in the writing of the paper. Patient consent Informed patient consent was received for the patient presented in the manuscript.