Beta-mannosidosis: lesions of the distal peripheral nervous system

Beta-Mannosidosis, an inherited glycoprotein metabolic disorder so far identified only in the caprine species, is characterized by deficiency of beta-mannosidase, oligosaccharide accumulation and excretion, neurovisceral cytoplasmic lysosomal storage vacuoles and central nervous system myelin and axonal lesions. In this investigation, transmission electron microscopy was used to study peripheral nerve elements in the gingiva of five affected goats and a control animal. Merkel and Schwann cells were vacuolated. Accumulations of dense bodies distended Merkel cell end plates and free-ending axons in the prickle cell layer as well as Pacinian corpuscle axons, and myelinated, unmyelinated, and demyelinated axons in the lamina propria. Unlike central nervous system myelin paucity, loss of peripheral nerve myelin was exclusively related to axonal dense body accumulation and enlargement. The identification of these lesions may facilitate detection of beta-mannosidosis in man and other species.