Gyrate atrophy of the choroid and retina is a genetic disorder, meaning it is caused by changes, or mutations, in a person's DNA. Understanding the genetic basis of this condition is crucial for diagnosis, management, and family planning.
The disease is caused by mutations in the OAT gene, which is located on chromosome 10. The OAT gene provides the instructions for making an enzyme called ornithine aminotransferase. This enzyme is responsible for breaking down the amino acid ornithine. When the OAT gene is mutated, the enzyme is either not produced or does not function correctly, leading to the toxic accumulation of ornithine that damages the eyes and other tissues. To date, researchers have identified over 60 different mutations in the OAT gene that can cause gyrate atrophy.
Gyrate atrophy is inherited in an autosomal recessive pattern. This means that for a person to develop the disease, they must inherit two mutated copies of the OAT gene—one from each parent. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene but typically do not show any signs or symptoms of the condition themselves. They are known as "carriers."
When two carriers have a child, there is a 25% chance with each pregnancy that the child will inherit two mutated genes and develop gyrate atrophy. There is a 50% chance the child will inherit one mutated gene and be a carrier like the parents, and a 25% chance the child will inherit two normal genes and be neither affected nor a carrier.
Because of the hereditary nature of gyrate atrophy, genetic counseling is highly recommended for affected individuals and their families. A genetic counselor can help families understand the inheritance pattern, assess the risk of passing the condition to future children, and discuss options for family planning. Genetic testing can confirm the diagnosis by identifying the specific OAT mutations, which can also be helpful in determining if the patient might respond to certain treatments, such as vitamin B6 supplementation. Patients and families should consult their healthcare provider to explore genetic testing and counseling services.