Percutaneous needle muscle biopsy in the evaluation of patients with suspected inflammatory myopathy.

OBJECTIVE

To determine the usefulness of a unique method of percutaneous needle muscle biopsy (NMB) in patients with suspected idiopathic inflammatory myopathy (IIM).

METHODS

The yield of percutaneous NMB was studied in 55 patients who were found to have a combination of clinical, laboratory, or electromyographic features of IIM.

RESULTS

A diagnosis of IIM was confirmed histopathologically in 29 patients (53%), other specific myopathies were found in 5 (9%), nonspecific myopathic changes were present in 11 (20%), and a neurogenic process was diagnosed in 3 (5%). Nonspecific changes or no abnormalities were present in 7 patients (13%). Followup of the 18 patients with nonspecific histopathologic findings disclosed that only 3 had a subsequent disease course compatible with IIM.

CONCLUSION

Percutaneous NMB is a safe, convenient, and relatively inexpensive method of muscle biopsy, with a high diagnostic yield for the pathologic confirmation of IIM. It should be considered as a primary method of acquiring muscle for histopathologic examination in the evaluation of suspected IIM.