Gyrate Atrophy oftheChoroid andRetina withHyperornithinemi a: Biochemical andHistologic Studies andResponse toVitamin B6

SUMMARY Fourpatients withhyperornithinemia andgyrate atrophy ofthechoroid and retina aredescribed. Invivoresponse tovitamin B6isdocumented inthree of thefourpatients bysignificant reduction offasting serumornithine and increase oflysine after oralB6supplementation. Oralglucose tolerance testing inonepatient resulted inmarked changes inserumornithine and lysine concentrations, inaddition tomildglucose intolerance. Histochemical staining ofpunchmuscle biopsies showed intracellular inclusions intype2 muscle fibers. Tubular aggregates, approximately 60nm indiameter and adjacent tothesarcoplasmic membrane, wereseenonelectron microscopy. Obligate heterozygotes hadameanserumornithine slightly higher than normal, butthere wasconsiderable overlap withthenormal range. Oral ornithine tolerance tests distinguished carriers fromcontrols inonlyoneof five cases. Deficient activity ofornithine ketoacid aminotransferase (OKT)incultured skinfibroblasts wasdocumented inallfourpatients. Approximately half-normal levels werefound inobligate heterozygotes. Invitro response to B6wasmanifest byincreased OKT activity atincreased concentrations of pyridoxal phosphate infibroblasts fromthepatients.