Biochemical and genetic characterization of an unusual mild PEX3-related Zellweger spectrum disorder.

Patients with PEX3 mutations usually present with a severe form of Zellweger spectrum disorder with death in the first year of life. Whole exome sequencing in adult siblings with intellectual disability revealed a homozygous variant in PEX3 that abolishes the normal splice site. A cryptic acceptor splice site is activated and an in-frame transcript with a deletion is produced. This transcript translates into a protein with residual activity explaining the relatively mild peroxisomal abnormalities and clinical phenotype.