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What is Alpha-Mannosidosis?

Alpha-mannosidosis is an inherited genetic disease that can cause many different health problems. These include mental retardation, skeletal abnormalities, hearing loss, muscle weakness, coarse facial features, and increased susceptibility to infection.

The severity of symptoms can vary widely among people with the disease. There are three main types of alpha-mannosidosis:

Type 1 - The mildest form, type 1, appears after the age of 10. People with type 1 typically do not have skeletal abnormalities, but do show muscle weakness. Their symptoms may be so mild as to be barely detectible. Symptoms tend to progress slowly.

Type 2 - In the moderate form known as type 2, symptoms appear before the patient reaches age 10. This form of the disease causes skeletal abnormalities and muscle weakness, but symptoms often progress slowly.

Type 3 - The severe form, type 3, the disease is usually fatal in childhood; some affected fetuses even die before birth. The symptoms appear early in infancy and progress rapidly.

While most of the people known to have alpha-mannosidosis fall into the moderate category, it may not be possible to predict which form of the disease a person will have based on their specific genetic mutation. Even siblings with the same genetic mutation may have symptoms that vary in severity.

All forms of alpha-mannosidosis involve some degree of intellectual disability, ranging from mild or moderate in type 1 to extreme in type 3. Combined with hearing loss, another symptom of the disease, this typically causes a delay in learning to speak, difficulties in pronouncing words, and a restricted vocabulary.

People with alpha-mannosidosis often experience an inability to coordinate their movements (ataxia) and general muscle weakness (myopathy). They often learn to walk later than other children and appear to be clumsy.

Many people with alpha-mannosidosis have immune deficiencies which leave them prone to frequent infection, particularly of the lungs, ears, and digestive system. Infections are most frequent in childhood.

Those with type 2 and 3 alpha-mannosidosis experience skeletal abnormalities that may include a reduction in bone density, deformed spine, bowed legs, and a deterioration of the bones and joints.

Some people with the disease experience hydrocephaly, a buildup of fluid around the brain. Some also have an enlarged livers and spleens, although these is not thought to cause health problems.

People with alpha-mannosidosis share certain facial characteristics, regardless of race. They have prominent foreheads, flattened nasal bridges, broad mouths, and protruding jaws.

Roughly 25% of people with the disease experience psychiatric problems distinct from their intellectual disabilities, often beginning in late puberty or early adolescence. These have included depression, confusion, anxiety, and hallucinations.

How common is Alpha-Mannosidosis?

Alpha-mannosidosis is extremely rare. It occurs in roughly 1 in 500,000 people worldwide. It can affect people from any race or ethnic group.

How is Alpha-Mannosidosis treated?

There is no treatment for the underlying cause of alpha-mannosidosis, however physicians can treat symptoms that arise in order to prevent complications and enhance the person's quality of life. Based on the person's symptoms, physicians often recommend a range of treatments such as antibiotics for viral infections; hearing aids; tubes to drain fluid from the middle ear; physical therapy to aid in movement; speech therapy; special education classes to facilitate learning; use of wheelchairs and other orthopedic aids; and/or an implanted shunt near the brain to help drain fluid buildup.

What is the prognosis for a person with Alpha-Mannosidosis?

People with milder forms of alpha-mannosidosis may live until their 50s. Those with the most severe forms, however, usually die before birth or in childhood.

People with alpha-mannosidosis tend to have more problems with infection during childhood. This often lessens by their 20s and 30s, when bone and muscle problems are more of a concern.


Genetics Home Reference

Explanations of an extensive number of genetic diseases by the U.S. government's National Institutes of Health.

The Arc


Phone: (301) 565-3842
Secondary Phone: (800) 433-5255

The International Advocate for Glycoprotein Storage Diseases

A group which supports and informs families affected by glycoprotein storage diseases, including alpha-mannosidosis.

Phone: 734-449-8222

Other names for Alpha-Mannosidosis

  • Lysosomal Alpha-D-Mannosidase Deficiency
  • Alpha-Mannosidosis
  • Lysosomal Alpha B Mannosidosis
  • Alpha-Mannosidase B Deficiency
  • Alpha-D-mannosidosis
  • Alpha-mannosidase Deficiency
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