[A case of anti-PL-7 antibody positive polymyositis with thrombotic microangiopathy]

A 65-year-old woman with a 17-year history of polymyositis and 8-year history of rheumatoid arthritis who was treated with a low dose of prednisolone and tacrolimus (Tac) was admitted to our hospital because of general malaise and hypertension. Blood tests showed thrombocytopenia, hemolytic anemia with fragmented erythrocytes, and hypercreatinemia. Based on these clinical features, she was diagnosed with thrombotic micro-angiopathy (TMA). Thrombocytopenia and hemolytic anemia with fragmented erythrocytes improved with the discontinuation of Tac and plasma exchange; however, hypertension and renal dysfunction persisted. TMA due to calcineurin inhibitor (CNI) nephropathy was suspected based on the histopathological findings of renal biopsy. However, the condition was atypical of a CNI nephropathy because the trough level of Tac was lower than that reported previously and renal dysfunction persisted after drug discontinuation. She had mild sclerodactylia and Raynaud's symptoms, although the diagnostic criteria for systemic sclerosis (SSc) were not satisfied. Moreover, the patient tested positive for anti PL-7 antibody. The relationship between anti PL-7 antibody and pathogenesis of SSc has been reported. In this case, it was suspected that CNI nephropathy worsened because of the potential basic factors of SSc. These findings indicate that TMA may occur in patients testing positive for anti PL-7 antibody who are treated with Tac.