Dermatomyositis (DM) and sarcoidosis are two idiopathic systemic disorders. Reports of patients with both conditions are extremely rare. Here we describe two patients who presented with DM and DM-associated antibodies, and later developed biopsy-proven sarcoidosis. There are increasing reports of the occurrence of sarcoidosis in the context of autoimmune diseases. These observations might imply similarities in the pathogenetic mechanisms.
Learning points: Sarcoidosis should be considered in patients with dermatomyositis (DM) presenting with enlarged lymph nodes. Contrary to the principle of Occam's razor, in this case one diagnosis does not rule out the other.The pathophysiology of sarcoidosis and DM involves both Th1 and Th17 inflammatory responses, which may explain the overlap of these two diseases.
Keywords: Sarcoidosis; auto-antibodies; dermatomyositis.