Alpha-mannosidosis

Alpha-mannosidosis is a rare inherited lysosomal storage disorder caused by mutations in the MAN2B1 gene, which makes the enzyme alpha-mannosidase. Without working enzyme, mannose-containing sugar chains build up inside lysosomes and damage cells in many organs and tissues. Affected people may have intellectual disability, distinctive facial features such as a large head and prominent forehead, and skeletal problems including reduced bone density. Other features include poor coordination, muscle weakness, hearing loss, cataracts, increased risk of infection and enlargement of the liver and spleen. Severity ranges from an early-onset form with rapid neurological decline to milder later-onset forms with survival into the fifties. It is estimated to affect about 1 in 500,000 people worldwide and is inherited in an autosomal recessive pattern.