Hyperornithinemia
Overview
Elevated levels of ornithine in the serum; sometimes associated with hyperammonemia and homocitrullinuria.
Symptoms
* High blood level of ornithine * Tunnel vision * Night blindness * Myopia * Progressive vision loss
Diagnosis
Newborn screening of dried blood spots using tandem mass spectrometry (MS/MS) is capable of identifying and quantitating Ornithine. Diagnostic evaluation can show abnormal levels of ornithine in plasma, cerebrospinal fluid and urine. An ornithine methyl ester is found in the urine of patients with gyrate atrophy and other conditions associated with hyperornithinemia.
Treatment
A few gyrate atrophy patients will respond to pharmacologic doses of vitamin B6 (pyridoxine) with increase in residual enzyme activity, partial reduction in plasma Ornithine and stabilization of vision. The slow progression of the degenerative changes in vision and the difficulty in measuring small changes in ocular function make evaluation of any therapy difficult. Additional approaches to therapy may be efficacious, including dietary reduction in Ornithine and administration of creatine.