To describe the clinical, laboratory, and histopathological characteristics of vasculitic myopathies.

While peripheral neuropathy is a common manifestation of systemic and nonsystemic vasculitides, myopathy has been rarely reported.

We performed an electronic chart review to identify patients with the diagnosis of vasculitis and myopathy seen between 2005-2019. We only included patients with either biopsy-proven vasculitic myopathy, or biopsy-proven vasculitis in non-muscle tissue, and concomitant inflammatory myopathy. 

We identified 11 patients with vasculitic myopathy. Three (27%) patients had a primary systemic vasculitis: 2 with eosinophilic granulomatosis with polyangiitis (EGPA) and 1 polyarteritis nodosa (PAN). Seven (64%) patients had a secondary systemic vasculitis: 3 with rheumatoid arthritis (RA), 2 systemic lupus erythematous (SLE), 1 anti-synthetase syndrome, and 1 Sjögren syndrome with Sarcoidosis. One patient had nonsystemic vasculitis. Median age-at-onset was 63 years (range 38-81), and median time to diagnosis was 2 months (1-6). Myopathy was the initial manifestation of vasculitis in 3 (27%) patients. The weakness was predominantly proximal in 7 and diffuse in 3. Five patients had distal sensory loss. One patient only had myalgia and exercise intolerance. Creatine kinase (CK) was elevated in only one patient (3620 U/L) while aldolase was elevated in 8 (80%) (2.9-13.9 U/L). EMG revealed short duration motor unit potentials in proximal and axial muscles in all patients, fibrillation potentials in 7 (70%) and superimposed peripheral neuropathy in 7 (70%). Muscle biopsy showed perimysial perivascular inflammation in 9/9 (100%) patients and vasculitis in 7 (78%), 3 of which demonstrated fibrinoid necrosis. Seven patients (78%) had necrotic and/or regenerating fibers. Treatment and survival outcomes will be presented at the conference.