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.