Electron microscopic studies of muscle biopsy in primary fibromyalgia syndrome: a controlled and blinded study.

Trapezius muscle biopsy was carried out in 21 patients with primary fibromyalgia syndrome (PFS) and 11 healthy controls, and assessed blindly by electron microscopy. Common findings in both the PFS and control groups were mild myofibrillar separation, papillary projections and subsarcolemmal accumulation of glycogen. However, the differences between the 2 groups were not statistically significant in any of the findings.