Pulmonary Manifestations of Idiopathic Inflammatory Myositis

Abstract

Idiopathic inflammatory myositis (IIM) is a connective tissue disorder characterized by muscular and extramuscular manifestations, in which lung involvement is a challenging issue. IIM is represented mostly by dermatomyositis and include antisynthetases syndrome. Various pulmonary features sometimes combined may be observed in IIM, like esophageal or respiratory muscle involvement and interstitial lung diseases (ILDs). ILDs are frequent and may have acute/subacute onset, especially in amyopathic forms. When faced with an acute ILD in critical care medicine, IIMs should be included in the gamut of diagnoses and lead to adequate investigations, including specific autoantibodies. Careful cutaneous examination should assess dermatomyositis features, namely skin ulcers illustrating MDA5-associated (Melanoma Differentiation-Associated protein 5) cutaneo-pulmonary syndrome, which portends a poor prognosis. The major ILD pattern is nonspecific interstitial pneumonia often associated with organizing pneumonia. ILD has a significant impact on morbi-mortality in IIM, with a high incidence of pneumomediastinum, complicating rapidly progressive ILD. Pulmonary hypertension is another prognostic feature of the disease. High-dose corticosteroids remain the cornerstone and first-line treatment of IIM-associated acute/subacute ILD, often associated with cyclophosphamide. Immunosuppressive drugs include the following: mycofenolate mofetil, azathioprine, or rituximab. Second-line treatment may comprise anticalcineurin drugs. This review aims to describe the clinical features of IIM-associated ILD and their actual therapeutic approaches, focusing on critical care issues.