ACOX1 and hyperinsulinemic hypoglycemia, familial, 4: Homozygous mutation in the ACOX1 gene is loss-of-function and causes peroxisome ACOX1 deficiency (OMIM#264,470), which is characterized by rapid and severe neurological damage as evidenced by hypotonia and seizures, enhanced reflexes, increased muscle tone, severe and recurrent seizures, progressive blindness and deafness, and VLCFA accumulation due to disturbances in fatty acid metabolism.