Diseases Associated with Generalized Enzyme Deficiencies

Peroxisomal biogenesis disorders (PBD) are represented by Zellweger's disease or cerebrohepatorenal syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD). Each is inherited in an autosomal recessive mode. To date, mutations in 12 genes (PEX) (with gene products peroxins) have been associated with PBD. Mutations in PEX1, located on chromosome 7, and in PEX6, located on chromosome 6, are the most common.

Defective synthesis of plasmalogen and defective oxidation of VLCFA are major biochemical defects. A reduced plasmalogen level and high VLCFA levels in plasma and cultured skin fibroblasts, and the absence of peroxisomes in the liver are diagnostic laboratory findings. Prenatal diagnosis is possible by performing the tests on amniocytes or cultured chorionic villi. MRI of the brain is helpful in revealing cortical and white matter abnormalities.

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