Detectable anti-MDA5 antibody before onset of clinically amyopathic dermatomyositis with rapidly progressive interstitial lung disease

Abstract

A 69-year-old woman was admitted to our hospital due to a two-week history of low-grade fever, dry cough and erythematous eruptions. Physical examination revealed facial erythema, Gottron’s papules, mechanic’s hands and fine crackles in both lower lung fields on admission. Muscle weakness, a heliotrope rash and the shawl sign were not observed. Chest X-ray and computed tomography showed rapidly progressive interstitial lung disease (RP-ILD) with focal areas of air-space consolidation and linear opacities bilaterally. Antimelanoma differentiation-associated gene five (anti-MDA5) antibody levels were elevated at 241 index. Although lacking clinical myositis, the skin lesions and interstitial lung disease suggested the development of dermatomyositis. She was diagnosed with RP-ILD in clinically amyopathic dermatomyositis, we started initial combination therapy with high-dose glucocorticoids, a calcineurin inhibitor and intravenous cyclophosphamide. However, she died on hospital day 15 despite aggressive immunosuppressive therapy. On autopsy, pathological findings of the lungs included diffuse alveolar damage in the exudative phase with hyaline membranes, oedema and interstitial acute inflammation. Moreover, we examined titres of anti-MDA5 antibody over time using a series of frozen serum samples before the onset of RP-ILD and found detectable low titres of anti-MDA5 antibody more than 2 years before disease onset by enzyme-linked immunosorbent assay and more than 4 years before disease onset by immunoprecipitation.

Keywords:

• Anti-MDA5 antibody
• clinically amyopathic dermatomyositis
• rapidly progressive interstitial lung disease
• pre-existence of disease-specific autoantibodies before onset

Conflict of interest

None.