Geneticists have discovered the biological basis for seven different subtypes of chronic fatigue syndrome which correspond with different symptom patterns in patients.
For a long time it has been suggested that not all cases of chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis (ME), are exactly the same and that there are in fact several subtypes of the disease. This view has been based on research findings which have shown for example that some patients have specific immune system or hormonal abnormalities while others do not.
A new study carried out by researchers at St George's Hospital, University of London, now provides genetic evidence that there are indeed variations of the disease and that these influence the symptoms that predominant in individual patients.
The results of the study are due to be officially presented at a ME/CFS conference in Cambridge, England which is being organised by ME Research UK and the Irish ME Trust.
The study involved 55 ME/CFS patients from both the US and UK along with 75 healthy controls. The researchers took blood samples from all participants and carried out genetic analyses.
Seven Subtypes of ME/CFS
Results showed seven distinct genetic patterns amongst the patients which were linked to specific symptom patterns.
- Type 1 - high levels of depression and anxiety as well as poor sleep and high degrees of pain.
- Type 2 - severe post-exertional fatigue, joint and muscle pains.
- Type 3 - mildest form of the disease.
- Type 4 - moderate levels of body pain and sleep problems
- Type 5 - most severe muscle weakness and predominance of gut problems
- Type 6 - associated with significant fatigue
- Type 7 - most severe form with high levels of pain, swollen glands and headaches.
It was found that types four and six were the most common forms of the condition.
Perhaps unsurprisingly it was found that most of the genetic markers in patients involved the regulation of the immune system. Strong evidence from other studies suggests that the immune systems of patients' remains activated after an initial trigger such as a viral infection. It is suggested that this itself is likely to cause symptoms and results in unbalanced defences which can allow other infectious agents such as bacteria and fungal organisms to cause various infections.
ME/CFS support organizations such as those organising the Cambridge conference are hoping that this information will lead to blood tests which will make diagnosis of the condition much easier and more accurate and will allow for tailoring of treatment based on the particular variant the patient is suffering from. Currently, diagnosis of ME/CFS is based purely on symptomology which is often difficult given that so many symptoms overlap with many other diseases.
Neil Abbot of ME Research UK said: "The discovery of a 'thumb-print' for the illness would be the single greatest advance that could be made because, at the moment, diagnosis is on the basis of a set of vague symptoms association with other illnesses.
"It's a hard illness to get a handle on, so a clinical test would be the single best way forward for everyone."
Lead researcher Dr. Jonathan Kerr said: "We must now determine what these sub-types represent, as they appear to be biologically meaningful, and discover their natural history and possibilities for treatment."
Dr. Kerr has been one of the most prominent researchers into the genetics of ME/CFS and is dedicated to developing a diagnostic test and effective treatments for the condition.
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