A joint team of researchers from Sweden, Italy, Greece and the Mayo Clinic in Minnesota claim to have unearthed a clue to a genetic basis for irritable bowel syndrome.

Irritable bowel syndrome (IBS) is a common intestinal disorder that affects about 15-20% of the Western world. In some countries, such as Sweden, IBS is the second highest cause of work absenteeism, after common colds.

Symptoms of IBS include cramping, abdominal pain, bloating gas, diarrhea and constipation.

Treatments for IBS tend to focus on relieving symptoms rather than addressing the root cause of the condition. This is because researchers have not found conclusive evidence to the origins of IBS. Instead, a variety of factors - from diet to past trauma - have all been considered as having some kind of influence.

In 2012, for instance, the US Department of Veterans Affairs implemented a new assessment rule for disability benefits taking into account a high incidence of IBS among veterans returning from Iraq and Afghanistan. This led doctors to wonder if IBS was caused by exposure to high levels of stress in conjunction with gastrointestinal infections from food or water.

Scientists from 19 European countries gathered together in 2013 to investigate the causes of IBS. Researchers from this network, known as GENIEUR (Genes in Irritable Bowel Syndrome Europe), included the Stockholm Karolinska Institutet in Sweden, who also contributed to the new study.

Gene mutation impairs function in an important sodium channel

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The researchers found that some IBS patients had a mutation of the SCN5A gene.

Examining potential genetic causes for IBS, the team behind the new study assessed 584 people with IBS and 1,380 control subjects.

The researchers found that 2.2% of the IBS patients had a mutation of the SCN5A gene. They also replicated the finding in 1,745 patients across four independent cohorts of IBS patients and control subjects.

The defect in the SCN5A gene interrupts a sodium channel, called Nav1.5, that is found in the gastrointestinal smooth muscle and pacemaker cells.

Investigating what treatments could be offered to IBS patients with this gene defect, the researchers found that a drug called mexiletine restores the function of the Nav1.5 sodium channel.

Using this drug, the team was able to reverse one patient's symptoms of constipation and abdominal pain.

Study author Dr. Gianrico Farrugia, who is also a Mayo Clinic gastroenterologist and director of the Mayo Clinic Center for Individualized Medicine, says:

"This gives us hope that from only treating symptoms of the disease, we can now work to find disease-modifying agents, which is where we really want to be to affect long-term treatment of IBS."

Meanwhile, new research from the University of Buffalo, NY, reports surprising results on how IBS patients rate their overall health. The researchers expected that the more severe a patient's IBS symptoms were, the more it would influence how they reported their health.

Instead, the study found that people who suffer from IBS find that social relationships, fatigue and coexisting medical problems have a more severe influence on how they regard their overall health than their gastrointestinal symptoms.