Sensorimotor Polyneuropathy in Light Chain Multiple Myeloma

Summary

The authors describe an adult onset sensorimotor polyneuropathy in a woman with light chain K-type myeloma. Neurophysiological investigation showed a severe reduction of conduction velocity of the peripheral nerve to the four limbs. A muscle and sural nerve biopsy were performed. Sural nerve displayed a severe loss of myelinated and unmyelinated fibers. No amyloid deposit was observed in vessels, perineurium and endomysium by electron microscopy examination. No onion bulb formation was present in nerve tissue, but many demyelinated fibers were surrounded by cir-cumferentially disposed Schwann cell processes without any interposition of collagen fibrils. Some fibers exhibit signs of active remyelination; axonal alterations were rarely seen. Collagen pockets were frequently observed among proliferated collagen fibrils. The mechanism of peripheral nerve lesions in various categories of multiple myeloma is till now an unsolved problem. In this case the unusual association with a light chain myeloma suggest that these immunoglobulins play a role in the pathogenesis of the polyneuropathy as supported by experimental studies.