TN 3 (02-10)
DI 23022.465 Neonatal Adrenoleukodystrophy
NALD; Neonatal ALD; Peroxisomal Biogenesis Disorder (PBD); Zellweger Syndrome Spectrum (ZSS)
Neonatal Adrenoleukodystrophy (NALD) is a leukodystrophy that causes damage to the myelin sheath, an insulating membrane that surrounds nerve cells in the brain (white matter). NALD also affects the adrenal glands and the testes. NALD belongs to the Zellweger spectrum of peroxisome biogenesis disorders (PDB, ZSS), is considered a moderately severe form and is caused by a mutation of several PEX genes. Symptoms include hypotonia, poor feeding, distinctive facial characteristics such as high forehead, a large anterior fontanelle, broad nasal bridge, crossed eyes, deformed ear lobes and skin folds, seizures and liver cysts with hepatic dysfunction, bony stippling of the patella and other long bones. The clinical course of NALD is variable and may include developmental delays, hearing loss, vision impairment, liver dysfunction, episodes of hemorrhage and intracranial bleeding.
TESTING AND CODING
Biochemical abnormalities detected in the blood and/or urine should be confirmed in cultured fibroblasts. The tests are used to detect accumulation of very long chain fatty acids (VLCFS) and whether the serum pipecolic acid is elevated (this finding helps differentiate NALD from X-ALD). Blood studies may detect adrenal insufficiency. MRI limited to the cerebellum may show defects in the white matter of the brain. ERG (electroretinogram) will be abnormal in those with retinal pigmentary degeneration. Hearing tests may be abnormal. Molecular genetic testing for mutations in the PEX genes.
NALD is a serious disease with most children dying as infants or before 3 years of age. While some children can be very hypotonic, others learn to walk and talk. The condition is often slowly progressive and may include degeneration of the myelin leading to loss of previously acquired skills and ultimately death. Children who survive in the first year and who have a non-progressive course have a 77% probability of reaching school age.
There is currently no cure for this disease. Treatment is symptomatic and supportive and may include: feeding tubes, hearing aids, cataract removal, vitamin K and other fat-soluble vitamin supplements and other liver dysfunction therapies, and anti-epileptic drugs to control seizures.
SUGGESTED PROGRAMMATIC ASSESSMENT*
Suggested MER for Evaluation: Plasma VLCFA abnormalities as outlined above or mutations in the PEX genes confirm a diagnosis of one of the PBD’s. If a PBD has not been confirmed by either biochemical or genetic testing, then a complete review of the clinical history, course and laboratory studies on which the disorder is suspected will need to be undertaken. Differentiation of NALD from the other PBDs will then depend on the other physical and laboratory findings. To evaluate the severity of this disease, a current complete examination will be needed.
Suggested Listings for Evaluation:
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*Adjudicators may, at their discretion, use the Medical Evidence of Record or Listings suggested to evaluate the claim. However, the decision to allow or deny the claim rests with the adjudicator.