A study of more than 2.5m adults has identified a genetic link between fibromyalgia and Huntington’s disease.
The research found an association between the long-term condition, which causes brain fog, fatigue and widespread pain, and the inherited neurological disorder.
Around 7,000 people in the UK are living with Huntington’s, a progressive condition that destroys nerve cells in the brain and affects movement, thinking and behaviour.
Charities estimate that up to 3m UK adults may have fibromyalgia, including Lady Gaga and Morgan Freeman, with thousands more thought to be undiagnosed.
Michael Wainberg, an investigator at the Lunenfeld-Tanenbaum Research Institute and the University of Toronto and co-senior author of the study, said: “This work changes how we think about fibromyalgia at a fundamental level.
“For decades, patients have been dismissed or told their pain is simply psychological. Our findings confirm the condition has a clear biological basis.”
An international team found the link after analysing genetic data from more than 2.5m adults, including around 55,000 with fibromyalgia.
Researchers identified 26 genetic changes linked to fibromyalgia, many involving brain and nervous system function.
The strongest signal was found within the huntingtin, or HTT, gene, the same gene that causes Huntington’s disease when faulty.
The researchers said the findings change how fibromyalgia is understood at a fundamental level.
Scientists identified the HTT gene as the cause of Huntington’s around 30 years ago and have studied it extensively since then.
The researchers said the new findings may also challenge long-held beliefs about fibromyalgia, including the idea that it is purely psychological.
The researchers said the results suggest fibromyalgia may be a disorder of the nervous system rather than an autoimmune disease, where the immune system mistakenly attacks the body.
However, a 2021 study by King’s College London suggested that many fibromyalgia symptoms are caused by proteins that make pain-sensing nerves more active.
Researchers said at the time: “The results show that fibromyalgia is a disease of the immune system, rather than the currently held view that it originates in the brain.”
Fibromyalgia most commonly affects middle-aged women and is usually diagnosed after the age of 25.
Charities estimate that between 1.8m and 2.9m people have the condition.
Experts not involved in the studies have said the true number may be higher because fibromyalgia can be difficult to diagnose.
The NHS says symptoms can vary between people, although the most common is widespread pain.
The condition can also cause heightened sensitivity to pain and bright lights, as well as stiffness.
Another commonly reported symptom is fibro fog, which can cause difficulties with memory, concentration and speech.
The new research also found genetic links between fibromyalgia and conditions including back pain, irritable bowel syndrome and post-traumatic stress disorder.
Researchers believe the conditions may share underlying nervous system problems, which could explain why they often occur together.
Frances Williams, a rheumatologist at TwinsUK, King’s College London and co-author of the study, said: “We know that chronic pain syndromes cluster together in individuals and families and are genetically similar.
“Targeting the shared mechanisms underlying them could potentially benefit a whole cluster of disorders.”
Despite the genetic links, researchers stressed that genes alone are unlikely to explain why someone develops fibromyalgia.
They said other triggers, such as a painful condition including arthritis, may be needed before fibromyalgia develops.
Nasa Sinnott-Armstrong, of Fred Hutch Cancer Center and the University of Washington in Seattle, said: “Understanding how genes, environmental exposures, and life events jointly contribute to risk of fibromyalgia syndrome is critical.
“Further research into triggers of fibromyalgia and corresponding changes to neural tissues will help understand what drives fibromyalgia and how to treat it.”
The team found no genetic differences between men and women, despite fibromyalgia being diagnosed around three times more often in women.
