Gyrate atrophy of the retina

Gyrate Atrophy of the Retina

Gyrate atrophy of the retina is a rare, inherited disorder that affects the retina, the light-sensitive tissue at the back of the eye. This condition is characterized by progressive degeneration of the retina, leading to vision loss.

Pathophysiology

Gyrate atrophy is caused by mutations in the OAT gene (ornithine aminotransferase), which is responsible for the production of the enzyme ornithine aminotransferase. This enzyme plays a crucial role in the metabolism of the amino acid ornithine. Mutations in the OAT gene lead to a deficiency of this enzyme, resulting in the accumulation of ornithine in the blood and other tissues, including the retina. The high levels of ornithine are toxic to the retinal cells, causing their degeneration.

Clinical Features

The condition typically presents in childhood or adolescence with symptoms such as:

• Night blindness (nyctalopia)
• Progressive loss of peripheral vision
• Tunnel vision
• Eventual loss of central vision

The characteristic feature of gyrate atrophy is the presence of sharply demarcated, circular areas of atrophy in the retina, which increase in size and number over time.

Diagnosis

Diagnosis of gyrate atrophy is based on clinical examination, family history, and genetic testing. An ophthalmologist may perform a dilated eye exam to observe the characteristic lesions in the retina. Additional tests may include:

• Electroretinography (ERG) to assess retinal function
• Visual field test to evaluate peripheral vision
• Genetic testing to identify mutations in the OAT gene

Management

There is currently no cure for gyrate atrophy, but management focuses on slowing the progression of the disease and addressing symptoms. Treatment options may include:

• Dietary restriction of arginine, an amino acid that can be converted to ornithine
• Vitamin B6 (pyridoxine) supplementation, which may help some patients with certain mutations
• Regular monitoring by an ophthalmologist

Prognosis

The progression of gyrate atrophy varies among individuals. While some may retain useful vision into adulthood, others may experience significant vision loss at an earlier age. Early diagnosis and management can help slow the progression of the disease.

Genetics

Gyrate atrophy is inherited in an autosomal recessive pattern, meaning that both copies of the OAT gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene but typically do not show signs and symptoms of the condition.

Research

Ongoing research is focused on understanding the molecular mechanisms of gyrate atrophy and developing potential therapies, including gene therapy and enzyme replacement therapy.

Also see

• Retinitis pigmentosa
• Choroideremia
• Leber congenital amaurosis
• Stargardt disease