Approximately 4% of individuals of South Asian ancestry carry a gene variant associated with increased risk of cardiomyopathy, a condition associated with heart failure. The magnitude of the risk, which is increased by about 7 times, is relatively high for a common variant, and carriers have a lifelong predisposition to heart failure suggests the study online this week in Nature Genetics.
Mutations in the gene encoding a certain cardiac protein had previously been shown to be associated with cardiomyopathy, which is characterized by weakness in the heart muscle. Kumarasamy Thangaraj and colleagues studied one of these mutations?a 25-base pair deletion?in two populations of Indian individuals with cardiomyopathy. They find that the deletion is associated with as much as a seven-time increased risk of cardiomyopathy. By assessing 28 unrelated Indian families, the team show that some carriers of the deletion manifest the disease by the third decade of life, and more than 90% of the oldest carriers in each family were affected. The deletion was occasionally observed in Southeast Asians, but was undetectable elsewhere in the world.
The authors show that the frequency of the deletion is significantly higher in southern and western India than in the north, a distribution that correlates with higher rates of heart failure in southern India. Despite being disadvantageous, they suggest that the deletion has risen to such a high frequency in South Asians because it typically has an effect after the age of reproduction.