OA15 A case series of idiopathic granulomatous mastitis patients and their immunosuppressive management
Authors: Islam Samsul , Stonelake Paul , John Holly 
Published: April 2024

Abstract

Background/Aims
Rheumatologists are experts in managing immunosuppression and are asked to supervise immunosuppression for non-rheumatic conditions. Thus, it is important to be aware of these conditions and the regimes required. Idiopathic granulomatosis mastitis (IGM) is a rare inflammatory breast condition which can have systemic manifestations including arthritis.

Methods
Our index case presented with peripheral ankle synovitis/tenosynovitis, struggling to weight bear, whilst being investigated for a breast mass. Breast US, mammogram and biopsy (acute and chronic inflammatory cells including multi-nucleated giant cells) were completed and there was little response to 3 courses of antibiotics. No mycobacteria were seen on microscopy, ZN stain negative, CXR normal, T spot negative and serum ACE normal. There was no rash and no conditions associated with a seronegative spondyloarthropathy. RF, anti-CCP and ANA were negative. A moderate course of prednisolone immediately resolved the peripheral arthritis, but high-dose steroids were required to reduce the breast mass. The mass recurred upon weaning prednisolone requiring the addition of azathioprine as a steroid-sparing agent.

Results
Our case series includes the immunosuppressive management of 3 other IGM patients: 1) 43-year-old referred after an 8 year history of alternating breast ‘abscesses’ and sinuses treated with courses of antibiotics to little avail. High dose prednisolone and methotrexate resolved the breast mass within a month. 2) 37-year-old referred with a 14 year history of breast masses and fistulae previously treated with surgery and antibiotics. Currently asymptomatic so commenced on methotrexate. 3) 39-year-old referred with a 3 year history of recurrent sterile breast abscesses previously managed with antibiotics, incision and drainage. Recent small masses had settled with NSAIDs.

Conclusion
IGM is a rare benign inflammatory breast disease of unknown aetiology, commonest in Middle Eastern populations, median age 30s. The most common presentation is a unilateral painful mass, which can ulcerate, fistulate and form abscesses. Management of IGM varies from expectant/topical steroids/NSAIDs to high dose steroids and DMARDs. A literature review shows that the usual starting dose of prednisolone is 40-60mg; the addition of methotrexate and azathioprine increases likelihood of successful treatment and allows for faster steroid tapering. Surgery for specific types of IGM can also be useful; for example, where there is duct granuloma, surgical excision can be curative. IGM can associate with arthritis, erythema nodosum, and episcleritis. One case series found that 14% of patients with IGM had concomitant arthritis.
Key points: In our local experience we have had four patients with IGM, all previously treated with antibiotics or surgical methods but subsequently diagnosed with IGM and referred for immunosuppressive therapy. Being a rare condition, we feel it’s important for clinicians to be aware of IGM and its link with inflammatory arthritis.

Disclosure
S. Islam: None. P. Stonelake: None. H. John: None.