ALPHA
MANNOSIDOSIS--Types
II and III
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ALTERNATE NAMES
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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
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DESCRIPTION
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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.
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DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM/ICD-10-CM CODING
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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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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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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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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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ICD-9: 278.8
ICD-10: E77.1
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PROGRESSION
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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.
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TREATMENT
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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.
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SUGGESTED PROGRAMMATIC ASSESSMENT*
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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
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Suggested Listings for Evaluation:
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DETERMINATION
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LISTING
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REMARKS
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Meets
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110.08
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112.02
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Equals
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* Adjudicators may, at their discretion, use the Medical Evidence of Record or the
listings suggested to evaluate the claim. However, the decision to allow or deny the
claim rests with the adjudicator.
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