Beta-mannosidosis is a rare lysosomal disorder that belongs to the group of oligosaccharidoses. It is characterized by the intracellular accumulation of a disaccharide due to the deficient activity of lysosomal beta-mannosidase. Identified in animals, it has only recently been recognized in human beings. So far only a dozen cases of this autosomal recessive disorder have been described, and it is still difficult to attribute symptoms to the disease. Although they are heterogeneous, clinical signs seem to be less severe than in animals, and include intellectual deficit, hearing loss, sometimes neurological symptoms such as hypotonia and convulsions, dysmorphic features, and repeated respiratory infections. Diagnosis can be established by assaying beta-mannosidase activity in peripheral blood leucocytes, plasma, or cultured fibroblasts, and by demonstrating the abnormal presence of a disaccharide in urine samples. Prenatal diagnosis is available. Currently, there is no specific treatment for the disorder.
Last update: February 2005