Definition: Beta-mannosidosis is an autosomal recessive lysosomal storage disease of glycoprotein catabolism caused by a deficiency of lysosomal beta-mannosidase activity. Most patients have mental retardation.
Synopsis
mild facial dysmorphism may occur
deafness
tortuosity of conjunctival vessels
tortuosity of conjunctival vessels
angiokeratoma
cytoplasmic vacuolization
thenar amyotrophy (rare)
mental retardation
speech impairment
hypotonia
seizures (rare)
demyelinating peripheral neuropathy, progressive (rare)
recurrent infections
LABORATORY
Decreased beta-mannosidase activity in plasma, fibroblasts, and leukocytes
Increased urinary disaccharides (mannosyl-N-acetylglucosamine)
Etiology
beta-mannosidosis is caused by mutation in the gene encoding beta-mannosidase (MANBA) (MIM.609489).