Symmetric sarcoid polyneuropathy: analysis of a sural nerve biopsy

A 20-year-old woman with sarcoidosis had uveitis, subacute symmetric sensorimotor neuropathy, and noncaseous granulomas in biopsies of gastrocnemius muscle and sural nerve. Morphologic studies of the nerve confirmed the electrodiagnostic impression of an acute axonal and demyelinating neuropathy. Of 100 teased myelinated nerve fibers, 15% contained myelin ovoids and 24% demonstrated segmental demyelination. Quantitative analysis showed a reduction in the numerical density of myelinated fibers. By electronmicroscopy, unmyelinated fibers were largely spared. The exact mechanism of nerve fiber damage was not determined, but a local effect of the granuloma seemed likely, because most lesions were found in the endoneurium.