Idiopathic granulomatous mastitis associated with erythema nodosum may indicate a worse prognosis

INTRODUCTION Idiopathic granulomatous mastitis (IGM) is a chronic inflammatory breast disease of unknown etiology, and erythema nodosum (EN) is a rare extramammary manifestation of this entity characterized by reddish, tender nodules of the lower legs. We aimed to investigate whether the association of IGM with EN has a role as a prognostic indicator. There are few case reports, and only 1 original article including 12 IGM patients with EN has been reported. METHODS We present 43 women with IGM coexisting with EN and 43 with a diagnosis of IGM only, who were randomly selected from 610 patients for a control group. To the best of our knowledge, this paper comprises the first comparative study of the coexistence of IGM and EN to be reported in the literature. RESULTS Our findings show that the association of IGM with EN indicates a more aggressive disease course. White blood cells, erythrocyte sedimentation rate, and C-reactive protein were significantly higher in the EN-positive group (P