Secondary immune thrombocytopenia with elevated serum ferritin in a patient with anti-MDA5 antibody-positive dermatomyositis

Dear Editor, macrophage activation is assumed to be involved in the pathogenesis of anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive dermatomyositis because macrophage activation markers such as serum ferritin and soluble CD206 are elevated and were reported to predict a poor prognosis of rapidly progressive interstitial lung disease (RP-ILD) [1, 2]. As a complication of macrophage activation, pancytopenia induced by autoimmune-associated haemophagocytic syndrome (AAHS) has been reported [3], but an association between macrophage activation and immune thrombocytopenia (ITP) secondary to anti-MDA5 antibody-positive dermatomyositis remains unclear. Here, we present a patient with anti-MDA5 antibody-positive dermatomyositis presenting with severe thrombocytopenia due to secondary ITP in accordance with elevated serum ferritin levels, in which intravenous immunoglobulin (IVIg) treatment combined with immunosuppressive therapy was extremely effective. A 69-year-old Japanese woman was diagnosed with dermatomyositis on the basis of heliotrope rash, Gottron’s sign, symmetric weakness of the upper and lower...