[Erythema nodosum during the course of idiopathic granulomatous mastitis]

Idiopathic granulomatous mastitis (IGM) is a benign, aseptic inflammatory disease of unknown origin, which must be distinguished from tumoral and infectious processes that affect the breast, including tuberculosis. IGM is a rare cause of erythema nodosum, but it is useful for dermatologists to be aware of this association.A 32-year-old nulliparous woman presented with erythema nodosum, arthralgia and fever. On examination, she had a firm and painful mass of 5cm in the right breast with retraction and axillary adenopathy. The breast lump developed gradually over the preceding 4 months. Although two biopsies showed no evidence of atypical cells, inflammatory areas and a granulomatous process were seen. Culture of breast tissue for mycobacteria was negative. A diagnostic of idiopathic granulomatous mastitis was made. Systemic corticosteroids led to a reduction in size of the mass, but relapse occurred in the contralateral breast on dose-reduction of the corticosteroids.IGM is a rare disease of unknown aetiology. Diagnosis is based on characteristic histological features and exclusion of other granulomatous diseases. Extra-mammary signs are rare and include erythema nodosum, arthralgia and episcleritis. Management is poorly codified.