What is the treatment approach for idiopathic granulomatous mastitis?

Treatment Approach for Idiopathic Granulomatous Mastitis

Initiate combination therapy with corticosteroids plus a steroid-sparing immunosuppressive agent (methotrexate or azathioprine) from the outset, as corticosteroid monotherapy has high failure and relapse rates.

Initial Treatment Protocol

Start prednisone at 30 mg/day (or 0.5-1 mg/kg/day) combined with either methotrexate or azathioprine from day one 1, 2, 3. The evidence strongly supports concurrent immunosuppression rather than sequential therapy, as this approach permits faster steroid tapering and reduces relapse rates 1.

Corticosteroid Dosing

• Begin with prednisone 30 mg/day as a single daily dose 1, 3
• Continue initial dose for 2-4 weeks until clinical improvement is evident 2, 3
• Taper gradually over 2-3 months based on clinical response 1, 2
• The addition of a steroid-sparing agent allows more rapid tapering without compromising efficacy 1

Mandatory Concurrent Steroid-Sparing Agent

Choose between methotrexate or azathioprine based on patient factors:

Methotrexate (preferred first-line option):

• Start at 5-15 mg orally once weekly 2, 4
• Add folic acid 1 mg/day supplementation 5, 6
• Low-dose methotrexate (5 mg/week) combined with prednisone 8 mg/day achieved 58.5% complete response and 17.6% partial response in IGM patients 4
• Screen for hepatitis B/C and obtain baseline liver function tests before initiating 6
• Requires reliable contraception in women of childbearing potential (teratogenic) 6

Azathioprine (alternative option):

• Target dose of 2 mg/kg ideal body weight in divided doses 1, 7
• Start at 25-50 mg/week with increments of 25-50 mg/week 7
• Combined prednisolone plus azathioprine achieved 73% complete response in IGM patients 1
• Check thiopurine methyltransferase level before initiating to screen for enzyme deficiency 8

Treatment Duration and Monitoring

• Continue combination therapy for 2-3 months initially 1, 2, 4
• Monitor for clinical improvement including reduction in breast mass size, decreased inflammation, and resolution of symptoms 1, 2
• Total treatment duration typically ranges from several months to ensure sustained remission 1, 3
• Consider shear wave elastography to objectively monitor tissue stiffness and guide dose adjustments, as a 20% or more reduction in elasticity values correlates with treatment response 9

Management of Treatment Failure or Relapse

If inadequate response after 2-3 months of combination therapy:

• Increase corticosteroid dose temporarily 1
• Consider switching from methotrexate to azathioprine or vice versa 2, 4
• Surgical drainage may be required for persistent abscess formation 1

Relapse occurs in approximately 13-27% of patients:

• Two of 15 patients (13%) relapsed in one series, requiring either surgical drainage or higher corticosteroid doses 1
• Restart or intensify immunosuppressive therapy rather than proceeding directly to surgery 1, 3

Critical Pitfalls to Avoid

• Never use corticosteroid monotherapy alone—this approach has high failure rates and frequent relapses after tapering or discontinuation 1, 2, 3
• Never delay initiation of steroid-sparing agents—start immunosuppression on day one, not after corticosteroid failure 1, 5, 6
• Avoid premature surgical intervention—surgery should be reserved for treatment failures or complications like abscess formation, not as first-line therapy 3
• Do not taper corticosteroids too rapidly—gradual tapering over 2-3 months reduces relapse risk 1, 2

Special Considerations

• Pregnant patients should receive prednisone monotherapy (30 mg/day) without methotrexate or azathioprine due to teratogenicity concerns 1
• Patients with contraindications to methotrexate (liver disease, alcohol use) should receive azathioprine instead 7
• Multidisciplinary management involving rheumatology, oncology, and gynecology is recommended given the autoimmune/inflammatory nature of the disease 2

Expected Outcomes

• Complete remission rates of 58-73% with combination therapy 1, 4
• Partial response in an additional 18% of patients 4
• Treatment failure requiring alternative approaches in approximately 23% of cases 4
• Significantly lower corticosteroid doses and side effects when using elastography-guided dose modification 9