Inclusion body myositis and sarcoid myopathy: coincidental occurrence or associated diseases

Inclusion body myositis (IBM) is a slowly progressive inflammatory myopathy characterized by selective weakness of finger flexors and quadriceps muscles commonly refractory to treatment. Another chronic inflammatory disorder, sarcoidosis, commonly involves muscle. The comorbidity of inclusion body myositis and sarcoid myopathy is rare. We describe clinical and muscle biopsy findings of a patient with sarcoidosis and inclusion body myositis. A 66-year-old man presented with a 6-year history of progressive, asymmetrical and selective weakness of the quadriceps, biceps and finger flexor muscles; he had a remote history of pulmonary sarcoidosis. A quadriceps muscle biopsy revealed a chronic inflammatory myopathy with ubiquitinated inclusion bodies, rimmed vacuoles, expression of major histocompatibility complex class I, numerous COX-negative fibers and TDP-43 cytoplasmic aggregates (features of IBM) and multiple non-necrotizing granulomata (feature of sarcoidosis). Clinical and histopathologic features of the current illness suggested the patient had sarcoidosis with inclusion body myositis overlap. This patient may represent the coincidental occurrence of both idiopathic inflammatory disorders. Alternatively, sarcoidoisis may promote the development of inclusion body myositis by a similar immune-mediated pathophysiologic process.