Gyrate atrophy (GA) of the choroid and retina is a rare autosomal recessive disorder that occurs due to deficiency of the mitochondrial
enzyme ornithine aminotransferase (OAT). Hyperornithinemia causes degeneration of the retina with symptoms like
myopia, reduced night vision and progressive vision loss. Our patient is a 10-year-old girl with impaired vision and
strabismus. As part of the metabolic work-up, plasma
amino acid analysis revealed significantly increased concentration of
ornithine (1039 μmol/L; reference interval 20 - 155 μmol/L). Molecular genetic analysis revealed homozygous mutation in exon 7 of the OAT gene that has not been reported previously (c.868_870delCTT p.(Leu290del)). This in frame deletion was predicted to be deleterious by in silico software analysis. Our patient was treated with
pyridoxine (
vitamin B6 in a dose of 2 x 100 mg/day),
low-protein diet (0.6 g/kg/day) and
L-lysine supplementation which resulted in a significant reduction in plasma
ornithine concentrations to 53% of the initial concentration and the ophthalmologic findings showed significant improvement. We conclude that
low protein diet and
lysine supplementation can lead to long-term reduction in plasma
ornithine concentrations and, if started at an early age, notably slow the progression of
retinal function loss in patients with GA. The effect of
therapy can be reliably monitored by periodical measurement of plasma
ornithine concentration. To our knowledge, this is the first report of
OAT deficiency in Croatia.