Clinical and prognostic significance of muscle biopsy in sarcoidosis

The main objective of this study was to evaluate the influence of muscle involvement on the clinical features, prognostic outcome, extrapulmonary organ, and endobronchial involvement in sarcoidosis patients. The second aim was to assess the diagnostic yield of muscle biopsy for the histopathologic identification of sarcoidosis.  Fifty sarcoidosis patients participated in the study. The patients were classified into two groups according to the histopathologic presence of non-caseating granulomatous inflammatory pattern of the muscle biopsy samples and were evaluated retrospectively in regard to clinical features, prognosis, extrapulmonary, and endobronchial disease involvement. Pathologic examination of the muscle biopsy samples revealed non-caseating granulomas in eighteen and myositis in seven patients compatible with sarcoidosis. The diagnostic yield of muscle biopsy for demonstrating non-caseating granulomatous inflammation was fifty percent. Patients with muscle sarcoidosis showed a worse prognosis and a more severe extrapulmonary organ involvement than the patients without muscle disease. Muscle biopsy was not statistically significant to delineate diffuse endobronchial involvement while it was suggestive for endobronchial disease clinically. The results of our study reveal that muscle biopsy appears to be a useful diagnostic tool along with its safety and easy clinical applicability. It is a rewarding utility to predict the prognostic outcome and extrapulmonary involvement in sarcoidosis patients. Positive biopsy on the other hand confirms the identification of sarcoidosis in patients with single organ involvement carrying an equivocal diagnostic clinical pattern. Muscle biopsy may be considered as the initial step for the final diagnosis of sarcoidosis in such cases.