In a girl with mannosidosis, who died at 3 1/2 years of age, histopathological and ultrastructural changes in the nervous system are described. A wide-spread neuronal storage evidenced by ballooning of the neuronal perikarya is the salient histological feature and the occurrence of electron-lucent storage vacuoles in neurons, astrocytes, endothelial cells and pericytes is the most striking ultrastructural feature of mannosidosis in the nervous system. By virtue of the deficiency of acidic alpha;-mannosidases A and B, the accumulation of mannose-containing oligosaccharides in tissues and the occurrence of storage vacuoles in various cells, mannosidosis is similar to various neuronal storage diseases associated with lysosomal enzyme deficiencies. In mannosidosis, the storage vacuoles in the neural and visceral tissues are alike with little variation in details and contain chiefly loosely dispersed, finely reticulo-granular material. The storage vacuoles in neurons in mannosidosis are, therefore, distinct from those in neurons in other lysosomal storage diseases such as Pompe's disease, various lipidoses and mucopolysaccharidoses. However, they resemble closely the storage vacuoles in neurons in fucosidosis and those in liver cells in various mucopolysaccharidoses.
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