Clinical findings at diagnosis and clinical course in Case 1. (a) Numerous papules on the back of metacarpophalangeal and interphalangeal joints. (b) Chest CT scan revealed band-like opacity and consolidations (indicated by a circle). (c) Skin biopsy revealed liquefaction and vacuolar degeneration at the dermal–epidermal junction (indicated by an arrow), and perivascular lymphocytic infiltration in the dermis (indicated by an arrowhead) (haematoxylin and eosin ×20). (d) Treatment was started including IV pulse MP (1000 mg/day, 3 days), PSL (1 mg/kg/day), TAC (3 mg/day), and pulse IVCY (12.5 mg/kg/day, 6 times). The value for the titre of serum anti-MDA-5 antibody and ferritin concentration was drastically improved in parallel with amelioration of skin and lung symptoms. In addition, the titres of KL-6 were decreased slowly.