Case report of anti‐transcription intermediary factor‐1‐γ/α antibody‐positive dermatomyositis associated with gastric cancer and immunoglobulin G4‐positive pulmonary inflammatory pseudotumor

Dermatomyositis is a rare connective tissue disease often associated with internal malignancy and interstitial pneumonitis. Serologically, various auto‐antibodies (Ab) are associated with dermatomyositis. Anti‐transcription intermediary factor‐1‐γ/α (TIF‐1‐γ/α) Ab was recently identified as an auto‐Ab and was observed mostly in cancer‐associated dermatomyositis. IgG4‐related disease is a newly described entity characterized by increased serum IgG4 levels and IgG4‐positive plasma cell infiltration with fibrosis in organs such as the pancreas and parotid gland. IgG4‐related disease also includes inflammatory pseudotumors in various organs. We report herein a 59‐year‐old Japanese man who had dermatomyositis complicated with a gastric cancer and an IgG4‐related pulmonary inflammatory pseudotumor. He manifested typical classical Gottron's papules on the fingers, V‐sign erythema on the chest, flagellate erythema on the back, nail fold bleeding and facial erythema. Serum levels of anti‐TIF‐1‐γ/α Ab were positive as assessed by immunoprecipitation assay. He also had bilateral swelling of the parotid gland, and an excised specimen of the lung showed inflammatory pseudotumor with IgG4‐positive plasma cells. As far as we know, this case is the first to report the association of IgG4‐related disease and TIF‐1‐γ/α‐positive dermatomyositis. Further accumulation of such cases is required to elucidate the mechanism of this association.