There is a common misconception that many genetic diseases are more common in Western countries than in India. For some, this has translated to an almost total disregard for some of the most common — and deadly — diseases in India.
A study conducted by MedGenome Labs, in partnership with Sir Ganga Ram Hospital in New Delhi, has found that, not only are disease-related genes more common in India than previously expected, they vary from those found in Western nations.
The study is, unfortunately, of limited scope, assessing a sample size of 200 unrelated individuals in the north Indian population over a period of 22 months. Of the 200 participants, 52 (26 percent) were found to be carriers of one or more rare genetic disorders. The title of rare disease in this regard is at least partially misleading. An estimated one in twenty Indians suffer from illnesses that fall under the classification of “rare diseases”. Children account for fifty percent of such cases.
Rare diseases affect around 350 million people worldwide. This figure includes roughly seventy million Indians. Each disease may individually affect just a few hundred, or a few thousand worldwide — many affect even less. The sheer number of different conditions that fall under the umbrella term of rare diseases, however, means that cumulatively these conditions affect hundreds of millions. Funding for each individual disease is often all but non-existent due to the limited impact of funding research into a disease affecting so few people.
Three percent of individuals within the survey were found to be carriers for Pompe disease, a rare genetic condition that impacts muscle function. This often leads to issues with both breathing and eating. This is a high rate that could indicate the Indian population to be far more vulnerable than others. However, due to the limited scope of the study, this could be an overestimate due to the small sampling size, warranting further investigations on a broader scale.
Other notable discoveries from the study indicated a statistical difference in the disease causing variants observed for disorders such as deafness, cystic fibrosis, Canavan disease, primary hyperoxaluria, junctional epidermolysis bullosa, galactosemia, and medium chain acyl CoA deficiency compared to Western populations.
Dr Sunita Bijarnia-Mahay, author and senior consultant at Sir Ganga Ram Hospital’s Institute of Medical Genetics & Genomics, said “this study brought surprises by detecting those genetic disorders like cystic fibrosis which were not thought to be common. In future, such next generation sequencing (NGS)-based screening tests will bring benefit to not only the young couples who would be planning a baby, but also the healthcare officials in charting out the prevention strategies for our Indian population.”
According to Dr Sheetal Sharda, a senior consultant in clinical genetics at MedGenome Labs in Bengaluru, “couples may not even be aware that they could be carrying a genetic variant, which could lead to their unborn child developing a genetic disorder. In most cases, carriers of a genetic disorder are asymptomatic and may have no family history and unfortunately their carrier status is often confirmed only after an affected baby is born.”
More genetic study is warranted within the Indian population. India represents almost twenty percent of the world’s population — and is on track to become the world’s most populous nation in the coming decades. Despite this, only 0.2 percent of fully mapped genomes in global databanks are of Indian origin.
Success has been had in the past regarding genetic studies of the Indian population. One Genome Wide Association Study (GWAS) found that there are six unique alleles present among the Indian population that causes a genetic predisposition to diabetes. This underlines at least part of the cause of high diabetes rates among Indians — other causes being lifestyle factors such as diets rich in sugar and sedentary lifestyles with a limited degree of exercise.
Genetics form an underlying component of disease that interacts in a complex manner with environmental factors and lifestyle choices to create a risk factor for many of India’s most common and life-threatening diseases. Diabetes is just one example. Heart disease — India’s most common cause of death — is another.
Knowledge of unique, or common genetic risk factors among India’s population is vital to shaping health programmes tailored to India’s population. With greater knowledge, and greater availability of genetic testing, countless lives could be saved by providing early warning of potentially life-threatening diseases.