“…The primary metabolic defect responsible for these manifestations is the deficiency of the acidic a-mannosidase A and B activities (a-D-mannoside mannohydrolase, EC. 3.2.1.24) (9,29,35), which results in the lysosomal accumulation of mannose-rich oligosaccharides in neural (34) and visceral tissues (I, 33) and in the urine (1, 31, 32, 46) of affected homozygous patients. Presumably this enzymatic defect also leads to the accumulation of other pathogenic glycoconjugate substrates with terminal a-mannosyl residues as evidenced by the recent finding of abnormal glycopeptides, rich in mannose, in cultured skin fibroblasts from a homozygote with mannosid?sis (47).…”