Program Operations Manual System (POMS)
TN 30 (08-20)
DI 23022.973 Nonketotic Hyperglycinemia
COMPASSIONATE ALLOWANCES INFORMATION
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NONKETOTIC
HYPERGLYCINEMIA |
ALTERNATE NAMES
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Glycine Encephalopathy; Hyperglycinemia Nonketotic; Isolated Nonketotic Hyperglycinemia;
NKH; Non-ketotic Hyperglycinemia
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DESCRIPTION
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Nonketotic Hyperglycinemia (NKH) is a genetic disorder characterized by abnormally high levels of glycine, an amino
acid that is one of the “building blocks” of proteins. Glycine also acts as a neurotransmitter,
which is a chemical messenger that transmits signals in the brain. NKH is caused by
mutations in the AMT and GLDC genes, resulting in shortages of an enzyme that normally
breaks down glycine in the body. This enzyme deficiency allows excess glycine to build
up in tissues and organs, particularly the brain. There are several forms of NKH,
which are distinguished by age of onset and severity of symptoms.
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DIAGNOSTIC TESTING, PHYSCIAL FINDINGS, AND ICD-9-CM/ICD-10-CM
CODING
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Diagnostic testing: A diagnosis of NKH is confirmed by:
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Laboratory findings of elevated plasma; and
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Urine and CSF (cerebral spinal fluid) glycine concentrations.
Physical findings: Individuals with NKH have:
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Movement disorders (ataxia);
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Hypotonia (weak muscle tone);
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Spastic diplegia (spasticity in the muscles of the legs, hips, and pelvis);
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Optic atrophy (damage to the optic nerves causing progressive vision loss and problems
with color vision);
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Developmental delays; and
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ICD-9: 270.7
ICD-10:
E72.51
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PROGRESSION
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Symptoms of NKH are present at birth with infants showing progressive lack of energy;
feeding difficulties; weak muscle tone; abnormal jerking movements; and life threatening
problems with breathing. Most children who survive these early signs and symptoms
develop profound intellectual disabilities and hard to treat seizures. Mortality is
associated with intractable seizures.
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TREATMENT
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Treatment of NKH is symptom specific. During the first two years of life, treatment
sodium benzoate to reduce plasma concentration of glycine. Other treatment consisting
of antiepileptic drugs for seizures; gastrostomy tube for feeding problems and gastroesophageal
reflux; and physical and occupational therapies to improve activities of daily living.
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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 and physical
findings; and
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Abnormally elevated levels of glycine in the blood and CSF; and
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Molecular genetic testing for mutations in the AMT and GLDC genes.
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Suggested Listings for
Evaluation: |
DETERMINATION
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LISTING
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REMARKS
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Meets |
11.02
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11.17
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12.02
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111.02
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111.17
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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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