Successful treatment of Anti-melanoma differentiation-associated gene 5 (MDA-5) antibody-positive dermatomyositis with rapidly progressive interstitial lung disease complicated by bilateral breast cancer following the additional tofacitinib: A case report.

Anti-melanoma differentiation-associated gene 5 (MDA-5) antibody-positive dermatomyositis (MDA5-DM) is known to cause rapidly progressive interstitial lung disease (RP-ILD). Cancer complications in MDA5-DM are less frequently reported compared to other forms of DM, though they do occur. The treatment strategy for DM with aspects of paraneoplastic syndrome is usually to treat the cancer first, if possible. However, surgery is difficult in the setting of respiratory failure and carries the risk of acute exacerbation of interstitial lung disease, as does chemotherapy and radiotherapy. The prognosis of MDA5-DM with RP-ILD has improved with initial immunosuppressive combination therapy, but certain cases remain refractory to treatment. Recently, the efficacy of janus kinase (JAK) inhibitors in refractory MDA5-DM cases has been reported. However, immunosuppressive therapies, including JAK inhibitors, may have negative effect on cancer progression. Here, we report a 48-year-old woman suffering from MDA5-DM with RP-ILD complicated by bilateral breast cancer. Due to respiratory failure, radical breast cancer surgery and chemotherapy could not be performed, so endocrine therapy and combined immunosuppressive therapy were first administered. However, the patient's condition was refractory to this initial treatment. Therefore, tofacitinib in combination with plasma exchange therapy was initiated, leading to an improvement in ILD, and bilateral mastectomy could be performed. One year later, MDA-5 antibody titers became negative, and glucocorticoid was successfully discontinued after two years. To date, three years have passed without recurrence of either MDA5-DM or breast cancer. To our knowledge, this is the first report of MDA5-DM complicated by breast cancer, as well as the first case of JAK inhibitor use for MDA5-DM with cancer. For curative treatment of MD5-DM with RP-ILD, if comorbid cancers are found, collaboration with oncologists to balance the efficacy and adverse events of MDA5-DM with RP-ILD therapy is essential in determining the appropriate type and timing of treatment, which could lead to a favorable outcome.