α ‐ and β ‐mannosidoses

Summary Clinical, pathological and biochemical findings in the mannosidoses are described. Family studies showed granulocyte‐rich white cell fractions to be the tissue of choice for carrier detection in β ‐mannosidosis. Metabolic labelling studies using [ 3 H] mannose demonstrated accumulation of Man β 1‐4GlcNAc in cultured skin fibroblasts from a patient with this condition. Alternative methods of egress from lysosomes were suggested for this compound by its secretion into culture medium and apparent reduction of storage with time in cultures. β ‐mannosidase deficient goats are not thought to be a true animal model of the human condition, as although they showed a similar enzyme deficiency, the clinical presentation is much more severe and the major storage material (Man β 1‐4GlcNAc β 1‐4GlcNAc) is different.