| Answer to PhotoQuiz 24 |
| Gyrate Atrophy of Choroid and Retina (OMIM # 258870) |
| Gyrate atrophy of the choroid and retina is an autosomal recessive disorder that results from the deficiency of ornithine ketoacid aminotransferase (OAT), an enzyme that catalyzes the transamination of ornithine to glutamate semialdehyde. The condition is characterized by hyperornithinemia. Night blindness starts in late childhood with gradual bilateral loss of vision progressing to total blindness by 40 to 60 years of age. There are sharply demarcated circular yellowish patches of atrophy in the periphery of the fundus at the onset and the areas of atrophy subsequently enlarge. Gyrate atrophy is caused by homozygous or compound heterozygous mutations in the OAT gene on chromosome 10q26. Restriction of arginine in the diet helps to control progression of the disease. |
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| Correct responses were given by: |
| 1. Himanshu Goel, Australia |
| 2. Aruna G, Bengaluru |
| 3. Beena S, Chennai |