A group of Korean researchers said they have confirmed a gene responsible for inherited retinal disorders (IRD) among Koreans.

IRD is a combination of several rare diseases that usually develops at a young age and progresses slowly over the lifetime. The patients gradually lose their sight, and most of them eventually lose their vision entirely due to continuous retinal cell degeneration.

The Seoul National University Bundang Hospital (SNUBH) Department of Ophthalmology and Seoul National University Hospital (SNUH) Department of Laboratory Medicine jointly conducted the study.

Currently, antioxidant therapy, artificial retinal transplantation, and stem cell therapy are being used to treat the disorder regardless of mutations, but the only viable treatment is gene therapy. Even when gene therapy is possible, only less than 1 percent of all IRD patients can be treated with it.

In the West, genetic abnormalities of these retinal diseases have been studied and known well. However, researches on Korean cases are still lacking, and the joint research team tackled the subject to find the causative gene for IRDs with 86 domestic patients, the team said in a news release on Wednesday.

The team studied and identified the gene responsible for the disorders by using the latest technique of gene analysis with the most number of patients who have been reported so far.

The study revealed that only 44 percent of the patients, 38 out of 86, possessed the causal gene for IRDs. Even among the patients with retinitis pigmentosa, the most common disorder among the IRDs, only 41 percent had the causative gene.

The causative genes could be quite diverse even in the same disorder. The patients can find a responsible gene only when they receive genetic counseling very actively and can receive gene counseling, too, the research team explained.

Differences were found in the type and frequency of causal gene mutations between Korean and Western cases. However, there were similarities between those of Korean and other Asian nations, including Japan.

The research and diagnosis environment for IRDs has been very poor until now, and our study has significance as a basic data for diagnosis and treatment for Korean patients with IRDs, SNUH Department of Ophthalmology Professor Woo Se-joon said.

Patients need to receive causal gene tests actively to provide the domestic medical communities with sufficient data, and a list of patients who can be treated. By doing so, clinical trials and new drug development in gene therapy will progress smoothly, he added.

Previously, only a few hospitals could diagnose the causative gene for IRDs and afford to test and treat IRD patients due to the high cost of genetic testing. Recently, however, the chance of diagnosis has increased as more hospitals are conducting genetic tests amid the lowered cost thanks to insurance benefits.

Also, the therapeutic opportunity for IRD patients is likely to get broadened, as the retinal pigment epithelium 65 gene (RPE65) therapy won approval from the U.S. Food and Drug Administration for the first time in the world.

Although we do not have a clear way to prevent IRDs at the moment, the prediction of risk and their early detection are developing through the discovery of family history and causative genes, Professor Woo said. Early diagnosis can prevent impaired vision by gene therapy and vision correction, and the patients will be able to choose appropriate jobs with social activities.

Also taking part in the research team were Professors Joo Kwang-sic and Park Kyu-hyung of SNUBH and Professors Seong Moon-woo and Park Sung-sup of SNUH.

The results of this study were published in the Journal of Korean Medical Science.

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