Alpha-mannosidosis

Alpha-mannosidosis is a lysosomal storage disorder. Lysosomes are the parts of a cell that break down and recycle used material. When the enzyme alpha-mannosidase is missing or weak, certain sugar-containing molecules cannot be broken down and build up in cells throughout the body.

Severity varies widely. Doctors often describe mild, moderate and severe types, but they blend into one another. The severe type appears in infancy and worsens quickly, while milder types may not be recognized until later childhood or adulthood and progress slowly.

Alpha-mannosidosis is caused by changes in both copies of the MAN2B1 gene. This gene carries the instructions for making the alpha-mannosidase enzyme.

It is inherited in an autosomal recessive pattern. Each parent usually carries one changed copy and has no symptoms. When both parents are carriers, each child has a 1 in 4 chance of being affected.

It is not caused by anything a parent did, and it cannot be caught from another person. A genetic counselor can explain what test results mean for brothers, sisters and future pregnancies.

Hearing loss and frequent infections, including ear infections, are common because the condition weakens the immune system. Developmental delays and learning difficulties are frequent. Facial features may slowly become coarser, with a large head and a prominent forehead.

Bones and muscles are affected too. People can develop a curved spine, other skeletal changes, muscle weakness and trouble with balance and coordination, called ataxia, that worsen over years. Over time, most people come to rely on a wheelchair, and some have anxiety, depression or other mental health symptoms.

Early signs such as hearing loss and infections are common in childhood, so diagnosis can take years. Alpha-mannosidosis is not part of routine newborn screening. A 2026 review found that both main treatments work better when they start early, before learning and thinking decline.

Families often manage years of appointments for hearing, ears, speech, learning and bones, sometimes long before a diagnosis. Children may need special education support, and adults may need help to stay independent.

Enzyme replacement means a weekly infusion, often at a hospital, for as long as it is continued. Because serious allergic reactions can happen, infusions are given where staff and equipment are ready to treat them. Travel and time away from school or work add up for families.

Families who are offered a transplant weigh a single but risky treatment against long-term infusions and ongoing symptoms. People with milder disease can live into later adulthood, often with growing needs for mobility and daily support.

Only a small number of people with alpha-mannosidosis have had a transplant. European transplant guidelines published in 2026 list it among the inherited conditions where a timely transplant is standard care. When a specialist team does consider one, usually for a young child before major decline, the cells come from another person.

Published cases used matched brothers or sisters, other matched relatives, unrelated volunteers, half-matched family members and cord blood. Brothers and sisters are tested first to make sure they do not have the condition themselves. The team chooses the donor that offers the best balance of match and safety.

A shortage of registry donors is not the main barrier for this condition. Earlier diagnosis and treatments that reach the brain are the bigger needs. Joining a registry still helps the many other patients who need an unrelated donor.