Peroxisomes are important parts of each cell in the body and are necessary for cell function, and for breaking down fats and chemicals, and getting rid of waste in the cells.
In people with peroxisome biogenesis disorder-Zellweger spectrum disorder (PBD-ZSD), alterations in one of the PEX genes lead to a loss of peroxisome function. Loss of peroxisome function can affect all major organ systems in the body.
People with PBD-ZSD may experience multisystem complications including neurological problems and seizures, delayed growth and development, hearing and vision loss, poor muscle tone, and skeletal and dental abnormalities.
Until recently, PBD-ZSD was viewed as three separate diseases, but we now know that PBD-ZSD is a set of disorders that form a spectrum of disease. This spectrum can range from mild (infantile Refsum disease), to moderate (neonatal adrenoleukodystrophy), to severe (Zellweger syndrome).
PBD-ZSD affects each person differently. How the disease impacts someone can vary with the age at which their symptoms first start to appear, the number of functioning peroxisomes they have, and the rate at which the disease progresses.
Individuals with Zellweger syndrome, at the severe end of the spectrum, develop signs and symptoms of the condition as newborns. These infants typically experience weak muscle tone (hypotonia), feeding problems, hearing and vision loss, liver dysfunction and seizures. Survival is usually not beyond the first year of life.
Individuals on the less-severe end of the spectrum may have hypotonia, vision problems, hearing loss, liver and kidney dysfunction, decreased bone mineral density developmental delay, and some degree of intellectual disability.
PBD-ZSD is estimated to occur in 1 in 50,000-70,000 births in the United States. It is inherited in an autosomal recessive pattern, meaning that a child is affected when each parent passes on one copy of the mutated gene.
Resources: UnderstandingPBD-ZSD.com; ZSDAlliance.com; “Zellweger spectrum disorders: clinical overview and management approach,” Orphanet Journal of Rare Diseases; National Organization for Rare Disorders.