Zellweger syndrome is one of a group of four related diseases called peroxisome biogenesis disorders (PBD), which are part of a larger group of diseases known as the leukodystrophies. These are inherited conditions that damage the white matter of the brain and also affect how the body metabolizes particular substances in the blood and organ tissues.
They are caused by defects in any one of 12 genes, termed PEX genes, that are required for the normal formation and function of peroxisomes (cell structures that break down toxic substances in the liver, kidneys, eyes, and brain, and synthesize fatty materials that are necessary for cell function). Peroxisomes are required for normal brain development and the function and formation of myelin, the whitish material that coats nerve fibers.
Zellweger syndrome is an autosomal recessive inherited disorder.
The PBDs are divided into two groups: Zellweger spectrum disorders and Rhizomelic Chondrodysplasia Punctata spectrum.
Zellweger syndrome is the most severe of three PBD disorders that have overlapping features; the other disorders being neonatal adrenoleukodystropsy and Infantile Refsum Disease, the mildest disorder.
Symptoms of the Zellweger spectrum disorders include:
- An enlarged liver
- Characteristic facial features such as a high forehead, underdeveloped eyebrow ridges, and wide-set eyes
- Neurological abnormalities such as mental retardation and seizures
Infants will Zellweger syndrome also lack muscle tone, sometimes to the point of being unable to move, and may not be able to suck or swallow. Some babies will be born with glaucoma, retinal degeneration, and impaired hearing. Jaundice and gastrointestinal bleeding also may occur.
The prognosis for infants with Zellweger syndrome is poor. Most infants do not survive past the first 6 months, and usually succumb to respiratory distress, gastrointestinal bleeding, or liver failure.
There is no cure for Zellweger syndrome, nor is there a standard course of treatment. Since the metabolic and neurological abnormalities that cause the symptoms of Zellweger syndrome are caused during fetal development, treatments to correct these abnormalities after birth are limited. Most treatments are symptomatic and supportive. Infections should be guarded against to prevent such complications as pneumonia and respiratory distress.