Alternative Names
alpha-D-mannosidosis; alpha-mannosidase B deficiency; alpha-mannosidase deficiency; lysosomal alpha B mannosidosis; lysosomal alpha-D-mannosidase deficiency; mannosidosis
Symptoms & Characteristics
Alpha-mannosidosis is a rare inherited disorder that causes problems in many organs and tissues of the body.
Signs and symptoms of alpha-mannosidosis include mental retardation; distinctive facial features; and skeletal abnormalities such as reduced bone density (osteopenia), thickening of the bones at the top of the skull (calvaria), deformations of the bones in the spine (vertebrae), bowed legs or knock knees, and deterioration of the bones and joints. Characteristic facial features include a large head, prominent forehead, low hairline, rounded eyebrows, large ears, flattened bridge of the nose, protruding jaw, widely spaced teeth, overgrown gums, and large tongue.
Affected individuals may also experience:
- Difficulty in coordinating movements (ataxia)
- Muscle weakness (myopathy)
- Delay in developing motor skills (such as sitting and walking)
- Increased risk of infections
- Enlargement of the liver and spleen (hepatosplenomegaly)
- A buildup of fluid in the brain (hydrocephalus)
- A clouding of the lens of the eye (a cataract)
- Psychiatric symptoms (such as depression, anxiety, or hallucinations)
Signs of alpha-mannosidosis may appear in infancy with rapid progression and severe neurological deterioration. Early-onset alpha-mannosidosis is typically fatal during childhood. In the most severe cases, an affected fetus may die before birth. Some individuals with alpha-mannosidosis experience milder signs and symptoms that appear later and progress more slowly. People with later-onset alpha-mannosidosis may survive into their fifties. The mildest cases may be detected only through laboratory testing and result in few if any symptoms.
Treatment
The management and treatment of alpha-mannosidosis is dependent upon the specific symptoms as well as the severity of symptoms.
How Common Is It?
Alpha-mannosidosis is believed to occur in approximately 1 in 500,000 people worldwide.
Genetics & Inheritance
Mutations in the MAN2B1 gene cause alpha-mannosidosis.
Alpha-mannosidosis is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. Two carriers have a 25% chance with each pregnancy to have an affected child.
Genetic Testing
Clinical genetic testing for alpha-mannosidosis may be available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
Support & More Information
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