ALPHA MANNOSIDOSIS--Types II and III

ALTERNATE NAMES

Alpha-D-Mannosidosis; Alpha-Mannosidase B Deficiency; Alpha-mannosidase Deficiency; Alpha Mannosidosis Types II/III Early Onset Forms; Lysosomal Alpha B Mannosidosis; Alpha B Lysosomal; Lysosomal Alpha-D-Mannosidase Deficiency

DESCRIPTION

Alpha Mannosidosisis a rare inherited metabolic storage disease caused by a mutation in the gene for alpha-mannosidase, an enzyme that normally breaks down sugars (carbohydrates) in lysosomes. Because of the mutation, sugars abnormally accumulate and impair the function of cells in the brain and other organs.

DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM/ICD-10-CM CODING

Diagnostic testing: A confirmed diagnosis is documented by abnormally low or absent levels of alpha-D-mannosidase enzymatic activity in white blood cells.

Physical findings:

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  Cognitive and motor developmental delay or intellectual disability;

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  Hearing loss;

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  Hepatosplenomegaly (enlargement of the liver and spleen);

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  Long bone and joint abnormalities;

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  Immune dysfunction leading to frequent infections;

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  Ataxia;

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  Facial abnormalities (e.g. prominent forehead, jaw, and flattened nose);

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  Distinctive facial features which may include widely spaced or unevenly developed teeth;

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  Thickened, enlarged tongue (macroglossia);

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  Prominent forehead;

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  Flattened nasal bridge;

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  Protruding lower jaw (prognathism);

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  Strabismus or crossed eyes;

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  Clouding (opacity) of the transparent outer covering of the eye (cornea);

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  Farsightedness (hyperopia);

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  Nearsightedness (myopia); and

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  Spinal abnormalities

ICD-9: 278.8

ICD-10: E77.1

PROGRESSION

Type III alpha mannosidosis is the most severe form, and signs and symptoms appear in infancy with rapid progression, severe neurological deterioration, and early death. In Type II, symptoms appear before age 10, and progressive deterioration is not as rapid as in Type III. For children with Type I, symptoms appear after age 10 and progress slowly; affected children have muscle weakness but not skeletal abnormalities, and they may live well into adulthood.

TREATMENT

There is no cure or treatment to alter the progression of alpha-mannosidosis. There are, however, symptomatic treatments that are used. For example, anticonvulsants can help to control seizures. Hearing aids improve ability to hear and communicate. Physical therapy may improve motor function, and assistive devices can aid with mobility. New and promising therapies for alpha mannosidosis include bone marrow transplantation, enzyme replacement, and gene therapy.

SUGGESTED PROGRAMMATIC ASSESSMENT*

Suggested MER for Evaluation:

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  Clinical history and examination that describes the diagnostic features of the impairment; and

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  Laboratory studies of alpha D-mannosidase enzymatic activity in white blood cells

Suggested Listings for Evaluation:

DETERMINATION

LISTING

REMARKS

Meets

110.08

112.02

Equals