A new study has found links between endogamy and a high prevalence of Ankylosing Spondylitis (AS) spine disease in the Reddy community.
Published Mar 06, 2025 | 7:00 AM ⚊ Updated Mar 06, 2025 | 7:00 AM
Synopsis: A recent study by the CSIR-Centre for Cellular and Molecular Biology (CCMB) has revealed a high prevalence of Ankylosing Spondylitis (AS), a debilitating spine disease, in the Reddy community. Generations of endogamous marriages have led to a concentration of the HLA-B*27:04 gene variant, which is significantly associated with AS, increasing the community’s susceptibility to the condition.
Among the most visible aspects of caste in modern India is the practice of endogamy, often prevalent even among the most educated, liberal and urbane.
This strategic practice of marrying exclusively within one’s caste is frequently presented as tradition and even as a form of cultural preservation.
But more often than not, it is about maintaining generational privilege, social and economic capital through deliberate social engineering that reinforces rigid boundaries between communities.
Possibly one of the biggest barriers to the elimination of caste as a practice despite earnest efforts for well over a century, endogamous marriages are now showing yet another serious consequence.
Years of research revealing higher rates of hereditary diseases in populations isolated by rigid marriage customs was augmented by a recent study by Hyderabad-based CSIR-Centre for Cellular and Molecular Biology (CCMB).
It revealed a high prevalence of Ankylosing Spondylitis (AS) in the Reddy communities of Andhra Pradesh and Telangana.
Ankylosing Spondylitis is a chronic inflammatory arthritis that primarily affects the spine, causing severe back pain, stiffness, and in advanced cases, fusion of the vertebrae, leading to a hunched posture.
It is part of the spondyloarthritis family of diseases and is strongly linked to the HLA-B27 gene, which plays a crucial role in immune system regulation.
The study found that the HLA-B*27:04 gene variant is significantly associated with AS in the Reddy population, increasing their susceptibility to the condition.
The study, published in the Journal of Genetics and Genomics, analysed 281 individuals from four South Indian populations (Kalinga, Kallar, Reddy, and Yadav) to understand how their genes are unique.
They examined the extent of inbreeding within these communities and identified new genetic variations that might affect health. They also studied how genes influence responses to medicines, helping explain why the same medicine works well for some people but not for others.
“We have analysed 281 high-coverage whole exome sequences from four anthropologically distinct populations. We examined several key factors, such as the extent of inbreeding and novel genetic variants in populations.
“We also looked at pharmacogenomic markers that influence drug metabolism to understand why different drugs seem to work differently in different populations,” said Dr Pratheusa Machha, lead author of the study.
The findings were striking: 13 percent of individuals in the Reddy population carried the HLA-B*27:04 allele, a much higher frequency than seen in the general population.
Think of your immune system as a security team patrolling your body, using special ID scanners (called HLA proteins) to check whether cells belong there or are invaders like viruses or bacteria.
HLA-B*27:04 is like a slightly faulty variant but sometimes, it mistakenly identifies your own healthy tissues – especially around your spine – as threats. When this happens, the immune system attacks these areas, leading to inflammation, pain, and stiffness, a condition known as Ankylosing Spondylitis (AS).
The study found that HLA-B*27:04 is far more common in the Reddy community due to generations of marriage within the same group.
This leads to the “founder effect,” where certain genetic traits become concentrated in the population over generations.
It is like a family heirloom that gets passed down more frequently when families marry within their own community, increasing the likelihood of Reddy individuals developing AS.
As the spine endures repeated immune attacks over time, the body tries to repair the damage by growing new bone.
However, instead of restoring normal function, this extra bone growth can eventually cause the vertebrae to fuse together, restricting movement and flexibility.
To further confirm the genetic link, researchers collaborated with the Krishna Institute of Medical Sciences (KIMS), Hyderabad, where they analysed hospital records of Ankylosing Spondylitis (AS) patients.
They found that KIMS Hospital in Hyderabad recorded approximately 140 AS patients from the Reddy population out of a total of 2,963 AS-positive cases. Notably, 28.6 percent (40 out of 140) of these Reddy AS cases were from a specific geographical region, which includes the sample collection area and nearby regions.
“This is an example of how endogamy in India is prevalent not only at the population level but also at the sub-population level, in small geographical regions,” said the authors of the study.
“We found a high incidence of Ankylosing Spondylitis in the Reddy community, who dwell in a specific geographical region of Andhra Pradesh,” said Dr Sarath Chandra Mouli Veeravalli, Rheumatologist at Krishna Institute of Medical Sciences, Hyderabad, and one of the study’s authors.
Additionally, researchers identified a significant number of disease-causing genetic variants, many of which are unique to specific populations.
The findings reveal several challenges for India’s healthcare system.
Dr K Thangaraj, the lead author of the study, said, “Our study forecasts the impact of endogamy in causing population-specific genetic diseases and drug responses. This emphasises the need for appropriate genetic screening, counselling, and clinical care for communities that are vulnerable to various health conditions.”
The study also identified new genetic variations that influence how individuals process certain medicines, which could help in developing personalised treatments.
These findings are especially significant for drugs such as tacrolimus, used to prevent organ rejection after transplants, and warfarin, a blood thinner that prevents clots.
“We observed genetic variations in the genes that alters the drug response, which differ across populations, and hence provide opportunity for developing targeted drug and improving health outcomes,” said Dr Divya Tej Sowpati, co-author of the study.
“This study reveals a major step towards our understanding of the genetic underpinnings for India’s unique genetic architecture. This is important in the development of more effective diagnostic and therapeutic strategies,” said Dr Vinay K Nandicoori, Director of the CSIR-Centre for Cellular and Molecular Biology, in a statement.
(Edited by Dese Gowda)
