Thrombotic microangiopathies (TMAs) rarely accompany polymyositis/dermatomyositis. We treated three patients with dermatomyositis combined with TMA. A literature review identified 13 previously reported cases. Exacerbation of myositis at the time of the TMA onset was observed in 62.5% of all patients, suggesting that the TMA onset may be associated with autoantibody production. We also found that cases of TMA with polymyositis/dermatomyositis often had a poor treatment response rate (37.5%). Furthermore, even if treatment was effective, the mortality rate associated with subsequent complications was high, and the survival rate was low (18.8%). Therefore, careful attention should be paid to patient management after TMA treatment.