A major genetic study involving more than 43,000 patients has uncovered a key genetic marker linked to severe forms of inflammatory bowel disease (IBD), raising hopes that doctors may one day identify high-risk patients earlier and prevent years of suffering.

The research, published on June 15, in The Lancet Gastroenterology & Hepatology, was led by scientists from the Wellcome Sanger Institute, the Francis Crick Institute, the NIHR IBD BioResource, and the UK IBD Genetics Consortium. After looking at genetic samples from over 100 hospitals, the team found a genetic pattern called HLA-DRB1*01:03 that seems to be closely linked to more severe forms of diseases like ulcerative colitis and Crohn's disease.

IBD affects more than half a million people in the UK alone and millions worldwide. These lifelong conditions cause inflammation and painful sores in the digestive tract, often leading to diarrhoea, stomach cramps, fatigue, and weight loss. While some patients experience only occasional symptoms, others face repeated flare-ups, major surgeries, and significant disruptions to daily life.

The researchers examined data from 43,762 patients, including 21,839 people with Crohn's disease and 21,923 with ulcerative colitis or unclassified IBD. Their findings revealed that around one in 20 patients carried the HLA-DRB1*01:03 variant. Genes are instructions inside the body's cells that help control how the body works. This particular genetic pattern is involved in the immune system, the body's natural defence against disease.

Patients carrying the variant were more likely to require advanced medicines, develop diseases around the anal region, and undergo surgery to remove part or all of the colon. Such outcomes often signal severe disease that is harder to control.

“We have undertaken the largest genetic study of IBD traits to date, involving data from more than 43,000 patients,” said Dr Qian Zhang, first author at the Wellcome Sanger Institute. “With this large cohort we were able to find that a combination of genetic variants known as HLA-DRB1*01:03 is linked to more severe disease.”

The findings echo a growing trend in medicine towards personalised treatment, where care is tailored to an individual's biological profile. Previous studies have identified dozens of genes linked to IBD risk, but predicting how severe the disease might become has remained a major challenge.

The findings offer hope to 26-year-old medical student Imogen, who underwent multiple surgeries after her diagnosis of ulcerative colitis as a teenager was changed to Crohn's disease. She said, "Identifying the correct treatment earlier could save a lot of time and suffering for people living with IBD."

Professor James Lee of the Francis Crick Institute said the discovery moves researchers closer to building reliable predictors of disease severity. If confirmed through future studies, a simple genetic test could help doctors identify vulnerable patients sooner, offer advanced treatments earlier, and improve their quality of life before irreversible damage occurs.