Peroxisome Biogenesis Disorder 1B (neonatal adrenoleukodystrophy)
Patient Information
Characteristics
Background and History
This disorder is sometimes called Refsum disease but it is entirely different in onset, course, and symptoms compared with the adult disorder of the same name. It belongs to a group of conditions called peroxisomal biogenesis disorders now considered to be part of the spectrum of Zellweger disorders, which are part of a larger group of diseases known as leukodystrophies.
Clinical Correlations
This condition presents in the first year of life, often with an enlarged liver and jaundice. Hearing loss and night blindness are also present early but these symptoms are difficult to detect in infants. Generalized floppiness is present in infants and children as well. Weakness and unsteadiness is noted when walking is first attempted. Inability to smell is nearly universal and mental retardation and developmental delays may be severe. Many do not survive infancy or childhood although some have lived into the 2nd and 3rd decades.
Genetics
Inheritance
This form of leukodystrophy, of disease of white matter of the brain, results from mutations in at least 3 genes. The inheritance pattern is horizontal as two mutations, one from each normal parent, are required for the disease to be manifest.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
This multisystem condition requires a team approach by neurologists, pediatricians and ophthalmologists for diagnosis. The prognosis is generally not good with high mortality in childhood. No effective treatment has been proven to work.
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