Peroxisome biogenesis disorders (PBDs) include the
Zellweger syndrome spectrum (PBD-ZSD) and
rhizomelic chondrodysplasia punctata type 1 (RCDP1). PBD-ZSD represents a continuum of disorders including
infantile Refsum disease,
neonatal adrenoleukodystrophy, and Zellweger syndrome. Collectively, PBDs are autosomal recessive developmental brain disorders that also result in skeletal and craniofacial dysmorphism, liver dysfunction, progressive sensorineural hearing loss, and
retinopathy. This results in the over-accumulation of
very long chain fatty acids and branched chain fatty acids, such as
phytanic acid. In addition, PBD-ZSD patients show deficient levels of
plasmalogens, ether-phospholipids necessary for normal brain and lung function. RCDP1 is caused by mutations in the
PEX7 gene, which encodes the PTS2 receptor. RCDP1 patients can develop large tissue stores of branched chain fatty acids, such as
phytanic acid, and show reduced levels of
plasmalogens. ==Enzyme and transporter defects==