NUDT15 c.415C>T (rs116855232) Allele Frequency and Estimated Thiopurine Metabolizer Phenotype Distribution in the Iranian Population: A Study Based on Public Genomic Data
This study analyzes public genomic data to reveal that the NUDT15 c.415C>T variant is prevalent in the Iranian population with significant inter-ethnic variability, suggesting that approximately 5.8% of Iranians may require thiopurine dose adjustments based on their metabolizer phenotype.
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Imagine a world where the same medicine that saves one person's life could dangerously harm another, simply because of a tiny difference in their genetic code. This is the reality of pharmacogenetics, the study of how our genes influence how we respond to drugs. Some medications, particularly those used to treat blood cancers and chronic gut inflammation, work by a delicate balance: they must be strong enough to fight the disease but weak enough to avoid destroying the body's ability to make new blood cells. For decades, doctors have known that a specific enzyme in the body acts as a safety valve, breaking down these drugs to prevent them from becoming toxic. However, in some people, a genetic variation causes this safety valve to work too slowly or not at all, leading to severe, sometimes life-threatening side effects. Understanding who carries these genetic variations is crucial for tailoring treatment to the individual, ensuring that life-saving therapy remains safe.
In a recent study, researchers turned their attention to the population of Iran to see how common these genetic variations are. While medical science has mapped these risks for many groups around the globe, the specific genetic profile of the Iranian people had remained largely uncharted territory. The scientists focused on a specific gene called NUDT15, which produces the enzyme responsible for managing these drugs. They were particularly interested in a single, well-known change in the genetic code, a tiny switch that flips a letter in the DNA sequence. This specific change is known to significantly increase the risk of dangerous side effects in people taking thiopurine drugs, a common class of medication for leukemia and inflammatory bowel disease. By looking at a large, publicly available database of genetic information from healthy Iranians, the team set out to count how many people carried this variation and to see if the risk was spread evenly across the country or concentrated in specific groups.
The researchers examined genetic data from over 1,200 unrelated individuals representing twelve distinct ethnic groups within Iran, including Persians, Azeris, Kurds, Baloch, and Turkmen, among others. They found that the genetic variation was far from rare. Across the entire group studied, about 3.16 percent of the gene copies carried this specific change. This frequency is surprisingly high, placing the Iranian population in a similar risk category to East Asian populations, where the variation is known to be common, and significantly higher than in European or African populations where it is nearly absent. However, the story was not the same for every community. The frequency of the variation shifted dramatically depending on the ethnic subgroup. In groups such as the Azeri, Lur, and Zoroastrian communities, the variation appeared in only about 1 percent of the gene copies. In stark contrast, among the Turkmen community, the frequency jumped to 10 percent, a rate even higher than the average seen in many East Asian populations.
These differences in genetic makeup translate directly into how people might process medication. Based on the genetic counts, the researchers estimated that roughly 94 percent of the Iranian population would process these drugs normally. However, about 5.3 percent of people were estimated to be intermediate metabolizers, meaning their bodies break down the drug more slowly than average, while a small but significant group of about 0.5 percent were estimated to be poor metabolizers, whose bodies struggle to clear the drug entirely. When combined, nearly 6 percent of the population carries at least one copy of the variation that could require a doctor to adjust the dosage of thiopurine drugs to prevent severe bone marrow suppression. The study also noted that when all the different ethnic groups were mixed together in a single analysis, the genetic patterns looked slightly unusual, a statistical effect caused by the fact that the country is made up of many distinct groups with different genetic histories, rather than a single uniform population.
The findings challenge the old assumption that this specific genetic risk is limited to East Asia or Latin America. The data suggests that in Iran, a country often viewed as a bridge between Europe and Asia, the risk profile is much closer to that of Asian populations than to its European neighbors. This is particularly important given that Iran faces a growing burden of the very diseases these drugs treat, including childhood leukemia and inflammatory bowel disease. The study concludes that testing for this genetic variation before starting treatment should be considered a standard part of care in Iran, just as it is in other parts of the world where the risk is known to be high. By identifying the 6 percent of patients who are at higher risk, doctors can personalize treatment plans from the very beginning, avoiding dangerous side effects and ensuring that the path to recovery is as safe as possible for every patient, regardless of their ethnic background.
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