Asymptomatic necrotizing myositis in a young male with progressive interstitial lung disease

Abstract

Necrotizing autoimmune myopathy (NAM) is a rare inflammatory process characterized by bilateral proximal muscle weakness and elevated creatinine kinase levels. It is one of the idiopathic inflammatory myopathies. It can be associated with anti-signal recognition particle (SRP) antibody which is commonly seen in middle-aged females. Classic findings on muscle biopsy include muscle fiber necrosis without inflammation. Pulmonary manifestations associated with anti-SRP NAM is rare, and often a challenging correlation to make as our understanding of inflammatory myopathies and interstitial lung disease is still evolving. There have been some associations of Anti SRP NAM with NSIP which responds to corticosteroids. We present a 29 year old male with asymptomatic NAM who presented with a combination of NSIP and pulmonary arterial hypertension (PAH). His PAH was responsive to oral vasodilator therapy however his interstitial lung disease (ILD) rapidly progressed to usual interstitial pneumonia (UIP) requiring lung transplantation. This case highlights 1) an extremely rare presentation of rapidly progressive NAM associated ILD in a young man, in which pulmonary manifestations occurred in the absence of myopathy, 2) The importance of doing a complete work up for interstitial lung disease, including diligent examination for myopathic features and obtaining CK levels, 3) Identifying that interstitial lung diseases can progress despite control of the underlying etiology with corticosteroids and immunosuppressives, 4) Recognition of pre capillary PAH in patients with disproportionally elevated pressures relative to their pulmonary findings, 5) The first report of treatment responsive pulmonary vascular disease associated with NAM, and 6) The importance of early lung transplantation evaluation.