Beta-mannosidosis is an autosomal recessive disorder caused by pathogenic variants in the gene MANBA. This condition varies in severity, and the age of onset ranges from infancy to adolescence. Almost all individuals have some level of intellectual disability. Behavioral concerns and problems include depression, extreme introversion, hyperactivity, and aggression. Other clinical manifestations include increased risk of respiratory and ear infections, impaired speech, hearing loss, hypotonia, seizures, peripheral neuropathy, distinctive facial features, and angiokeratomas (benign growths of capillaries). Life expectancy may be reduced depending on the severity of symptoms. No clear genotype-phenotype correlation has been established.
For information about carrier frequency and residual risk, please see the residual risk table.