IFIH1 and Hermansky-Pudlak syndrome: Patients with anti-MDA5 antibody-positive DM have elevated serum ferritin levels, which may be associated with the ILD activity in DM.[10] Hyperferritinemia in rheumatic diseases may be suggestive of HPS but is difficult to detect in anti-MDA5 antibody-positive DM due to the association of hyperferritinemia with ILD activity and the rare coexistence of DM and HPS.