Treatment of a case with anti-MDA5 antibody positive clinically amyopathic dermatomyositis complicated with stomach cancer and colon cancer

A 74-year-old woman noticed an edematous erythema on the right upper eyelid two months before her first medical examination, and slight fever, arthralgia and edematous erythema on the forearms and palms around the time of the first medical examination. She presented with typical skin lesions of dermatomyositis including Gottron’s signs and a heliotrope rash without any abnormal muscle symptoms. An examination by gastrointestinal endoscopy and a computed tomography scan of the chest revealed that she was complicated with stomach cancer (Stage ⅠA), colon cancer　(Stage Ⅰ) and interstitial pneumonia (IP). She was diagnosed with anti-MDA5 antibody-positive clinically amyopathic dermatomyositis (CADM) complicated with two cancers. Because the IP became aggravated, she was treated with corticosteroids at an initial dose of 1 mg/kg/day and immunosuppressive therapies. Tacrolimus was discontinued due to thrombocytopenia, and she also had an allergic reaction to cyclophosphamide. The administration of azathioprine at a dose of 75 mg/day prevented the exacerbation of IP. We were able to be taper the dose of corticosteroids, and endoscopic stomach surgery and abdominal rectal surgery was performed. The anti-MDA5 antibody is a characteristic myositis-specific autoantibody associated with CADM and IP, which may cause a poor prognosis. CADM complicated with malignancy occurs less frequently than similarly complicated dermatomyositis and, to the best of our knowledge, this is the first case of CADM complicated with two cancers.