Test Details: Deficiency of lysosomal enzyme alpha mannosidase is inherited in an autosomal recessive manner. This is a genetic disorder of metabolism characterised by immune deficiency, facial and skeletal abnormalities, hearing impairment and mental retardation. The diagnosis of alpha-mannosidosis is established in a proband by identification of deficient acid alpha-mannosidase enzyme activity in peripheral blood leukocytes or other nucleated cells such as fibroblasts.