Pneumopathie infiltrante diffuse associée à une dermatomyosite amyopathique avec auto-anticorps anti-MDA5

Abstract

Amyopathic dermatomyositis associated with anti-MDA5 autoantibodies is a rare and very recently described clinical entity. A 58-year-old woman was admitted with subacute onset of dyspnea (NYHA class IV) associated with cough, oligoarthritis of the wrists, myalgia and intermittent fever. Examination demonstrated skin lesions with heliotrope rash, Gottron's papules, "mechanics hands", and basal inspiratory crackles on lung auscultation. Pulmonary function tests showed a restrictive ventilatory defect, with decreased carbon monoxide diffusion capacity and marked hypoxemia (PaO2 61 mmHg). The chest high-resolution computed tomography appearances were consistent with organizing pneumonia. Bronchoalveolar lavage differential cell count demonstrated 22 % neutrophils. Serum creatine kinase and electromyography were normal ; the serum ferritin level was elevated. Antinuclear antibodies were present and anti-MDA5 autoantibodies were identified. Significant improvement was obtained with systemic corticosteroids, later converted to mycophenolate mofetil as a steroid-sparing agent. Amyopathic dermatomyositis associated with anti-MDA5 autoantibodies shares some characteristics with those associated with anti-synthetase antibodies. Muscular involvement may be mild or absent. Early diagnosis and treatment may improve outcome.