IFIH1 and dermatomyositis: Serum ferritin levels tend to decline approximately 2 weeks after the administration of IVCY, which is a key drug in the treatment of anti-MDA5 Ab-positive DM patients.[17] Because an earlier initiation of the treatment affects the mortality rate, PE with immediate effects would be a better strategy for RPILD patients with anti-MDA5 Ab-positive DM until IVCY treatment is effective.