Background/aim: Idiopathic granulomatous mastitis (IGM) is a rare, chronic inflammatory disease of the breast. Erythema nodosum (EN) is a rare extramammary manifestation of IGM. The purpose of this study is to determine the clinical and demographic characteristics of 11 IGM and EN patients and to evaluate the efficacy of methylprednisolone treatment. Materials and methods: In our series, ten patients had EN bilaterally, whereas one patient had a lesion of the right pretibial area. The mean age of the patients was 35.5 years (range: 29-45 years). IGM and EN were diagnosed by the necessary serological, microbiological, radiological, and histopathological examination. After diagnosis, methylprednisolone was started in the first week at 0.8 mg/kg daily for treatment. The weekly dose was tapered to 0.1 mg/kg daily over 8 weeks.Results: We started with the treatment of methylprednisolone, and in all our cases the initial response was excellent. In 2 weeks the IGM symptoms had markedly declined, while signs of EN disappeared completely. Patients were followed for an average of 60 months after treatment. None of the 11 patients had recurrence.Conclusion: We herein report a rare series considering IGM cases complicated by EN. Few such cases have been reported in the literature. We advocate for an initial trial of methylprednisolone treatment, which proved to be very successful in our patients.