Acute Overlap Syndrome with Myopathy Associated with Anti-signal Recognition Particle Antibodies and Sarcoidosis

Objective: To present an acute overlap syndrome of anti-signal recognition particle antibody (anti-SRP) myopathy and systemic sarcoidosis Background: NA Design/Methods: Case report Results: A 61-year-old African-American man presented with a 3 week history of progressive dyspnea and generalized weakness. Two years earlier he had been diagnosed with systolic heart failure of unknown etiology (ejection fraction of 20%). Examination was notable for generalized proximal to distal weakness. Diagnostic evaluation revealed non-caseating granulomas (NCG) on cardiac biopsy and creatine kinase of 8,889 IU/L. Renal function, electrolytes, complete blood count, thyroid hormone, erythrocyte sedimentation rate, and antinuclear antibodies were normal. Electromyography revealed a severe generalized irritative myopathy. Serologies for HIV and 3- hydroxy-3-methylglutaryl coenzyme A reductase antibody were negative but the myositis panel showed high-titer anti-SRP antibodies (>100 SI). Subsequent muscle biopsy revealed scattered necrotic and regenerating fibers with a paucity of inflammation and no NCG. Patient was treated with pulse dose IV methylprednisolone followed by IV immunoglobulin and steroid taper. Within days of treatment, the patient showed significant improvement in strength and mobility. Conclusions: The patient’s clinical phenotype, autoantibodies, and histological data are characteristic of SRP myopathy, which is characterized by rapidly progressive proximal muscle weakness, scattered necrotic muscle fibers and scant inflammation. In contrast, sarcoidosis myopathy typically presents with insidious muscle weakness along with NCG and diffuse inflammation on biopsy. Although asymptomatic muscular involvement in sarcoidosis is common (50% of cases at post-mortem), clinically apparent myopathy is seen in only 1% of cases. This is the first reported case of overlap syndrome with systemic sarcoidosis and SRP myopathy, and highlights the importance of considering other potential etiologies of rapidly progressive myopathy despite histologically-proven systemic sarcoidosis. Disclosure: Dr. Daley has nothing to disclose. Dr. Opala has nothing to disclose. Dr. Tavee has nothing to disclose.