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A6475 - A Case of Rapidly Progressive Interstitial Pneumonia in Association with Amyopathic Dermatomyositis with Elevated Titers of Anti-MDA-5 Antibody, Successfully Treated with Rituximab in Addition to Standard Immunosuppressive Therapy
Author Block: T. Nishizawa1, G. Kida1, Y. Tsukahara1, K. Emoto1, E. Tsumiyama1, S. Kriiwa1, T. Oba1, R. Kawabe1, S. Sato1, K. Akasaka1, H. Ishii2, M. Amano1, H. Matsushima1; 1Respiratory Medicine, Japanese Red Cross Saitama Hospital, Saitama, Japan, 2Respiratory Medicine, Kyorin University Hospital, Mitaka city, Japan.
A 70-year-old female was admitted to our hospital because of cough, dyspnea on exertion, and rashes on the anterior chest for about 2 months. On admission, her body temperature was 37.3ºC, blood pressure was 143/68 mmHg, respiratory rate was 16 breaths per minute, pulse rate was 82 beats per minute, and oxygen saturation was 96% on nasal oxygen at a flow rate of 2 L per minute. Fine crackles were audible in the lower lung fields bilaterally. Skin findings confirmed Gottron’s papules, Mechanic’s hands on the first and second fingers of both hands, V-neck symptoms, paronychia erythema, and elbow head erythema. Laboratory tests showed mildly elevated CPK (269 IU/l), KL-6 (714 U/ml), and SP-D (35.7 ng/ml). Autoantibodies were negative, including anti-ARS antibody. However, titers of anti-MDA-5 antibody were very high. Chest X-ray showed diffuse infiltrative shadows in bilateral lung fields. Chest CT findings revealed non-segmental infiltrative opacities with a sub-pleural distribution. Therefore, we diagnosed her clinically as having amyopathic dermatomyositis with rapidly progressive interstitial pneumonia. After admission, we treated her with steroid pulse therapy, followed by steroid therapy and tacrolimus. However, since her respiration gradually deteriorated and eruptions did not improve, intravenous cyclophosphamide pulse therapy was added on the 22nd and 36th hospital days, although with further deterioration in her respiration and radiological findings. We decided to treat her with four weekly infusions of rituximab (375 mg/m2). After the first administration of rituximab, her eruptions markedly improved and respiration also improved. Further therapy consisted of tapering of steroids, maintenance of tacrolimus at 4 mg per day, and rituximab. With this, her respiratory failure gradually improved, and chest CT findings showed improvement of consolidation in both lower lung lobes. She was discharged from the hospital on the 140th day. We believe that rituximab therapy was very effective for treating rapidly progressive interstitial pneumonia in our case. Rapidly progressive interstitial pneumonia associated with amyopathic dermatomyositis is known to have an extremely high mortality rate and poor prognosis. Anti-MDA-5 antibody is associated with the risk of rapidly progressive interstitial pneumonia, as well as a characteristic cutaneous phenotype, but not with myositis. Many cases of amyopathic dermatomyositis are often resistant to combination immunosuppressive drug therapy. However, in survivors, further immunosuppressive therapy, including rituximab at an early stage, leads to clinical improvement and a better prognosis. In patients with dermatomyositis, especially amyopathic dermatomyositis, rituximab therapy, although challenging, may be useful for treating interstitial pneumonia.