Fibrocellular non‐specific interstitial pneumonia with favourable prognosis in clinically amyopathic dermatomyositis

We report the case of a 49‐year‐old man who experienced dry cough and itching eruption for 2 months. The patient had Gottoron's sign, mechanic's hand, and high levels of serum Krebs von den Lungen‐6 and surfactant protein D, but was negative for anti‐aminoacyl transfer RNA synthetase antibodies. High‐resolution chest computed tomography revealed subpleural band‐like or patchy consolidation with predominance in the bilateral lower lobe. Bronchoalveolar lavage fluid showed increased total cell counts with lymphocytosis. Video‐assisted thoracic surgery specimens were consistent with fibrocellular non‐specific interstitial pneumonia (NSIP) accompanied by accumulation of lymph follicles within fibrosis. After combination therapy with prednisolone and cyclosporin A, his clinical symptoms improved gradually. Finally, an anti‐melanoma differentiation‐associated gene 5 (anti‐MDA5) antibody was detected. No relapse of the disease has been observed for 2 years. This is the first reported case in which anti‐MDA5 antibody‐positive clinically amyopathic dermatomyositis associated with fibrocellular NSIP characterized by subacute onset was found to have favourable prognosis.