Many of you will have seen the news this week on this site and elsewhere that seven subtypes of chronic fatigue syndrome (ME/CFS) have been catergorized based on new genetic research.
This is fascinating stuff. Not only does it give us a deeper understanding of what is going on in ME/CFS and offer the hope of diagnostic tests and treatments in the not too distant future, but it also puts another (rather large!) nail in the coffin of the idea that the disease is psychological in origin. Let's face it, this idea should have been buried years ago but its proponents (mainly psychiatrists) are a stubburn lot!
ME/CFS has always been a highly puzzling illness for researchers because despite obvious commonalities between patients, chronic fatigue being the obvious one, there are also many differences. These can be grouped into different areas of investigation:
A proportion of patients can trace the start of their illness to an acute viral illness, myself included. I developed a flu-like illness in November 1990 which would seem to clear up after a few days only to return the following week. This went on until the New Year when I realized I was no longer acutely ill but didn't feel healthy either. I was diagnosed with ME/CFS 4 months later after tests failed to turn up anything else. This pattern doesn't appear to be the same for all patients however. Some report various of factors triggering their illness such as an extremely stressful event such as the death of a loved one, divorce etc. In a sizeable number of patients the illness doesn't start suddenly at all but develops slowly over time.
Studies have often found abnormalities in levels of certain neurotransmitters such as serotonin, dopamine and noradrenaline (norepinephrine) in ME/CFS patients. The trouble is that the results are often conflicting with some patients having abnormally high levels of serotonin and others low levels for example. I personally suffer from S.A.D. as part of my illness which tends to suggest my serotonin levels may be low rather than high, during the winter months at least. Other neurological abnormalities include altered blood flow to the brain and a condition known as neurally mediated hypotension, or orthostatic intolerance, which results in a lack of blood flow to the brain, usually when standing up or when standing for long periods. This results in feeling dizzy, lightheaded, faint and wobbly and occurs because the brain fails to increase blood pressure so that enough blood reaches the brain when standing upright. Again not everyone with ME/CFS seems to suffer from this, at least not to the same degree.
A number of studies have found low levels of the stress hormones cortisol and DHEA which are produced by the adrenal glands. This could account for ME/CFS patients' inability to get going in the morning and poor tolerance for exercise and stress. The picture is not clear however as the low cortisol levels seem to be more prevalent amongst women and giving cortisol replacement treatment to those with low cortisol does not work consistently.
Studies have found various abnormalities of the immune system with some aspects being overactive and some underactive. Some types of immune cells (e.g. natural killer cells) are often low in number but no consistent picture of immune dysfunction has emerged. In addition ME/CFS patients are more likely to have allergies than the general population but not all sufferers have allergies by any means. Some studies have found autoantibodies (antibodies that attack the person's own body tissues) in patients but results have been inconsistent.
ME/CFS has significant overlap in symptoms with other poorly understood conditions. Many people with ME/CFS are also diagnosed with fibromyalgia, irritable bowel syndrome (IBS), and multiple chemical sensitivity (MCS). They are much more likely to suffer from these conditions than the general population. Again this is not always the case and ME/CFS patients may have none of these other conditions.
All of these findings have lead most researchers to conclude that ME/CFS is not a single disease with a single cause but rather a group of diseases with a common base but a different expression of symptoms and biochemical abnormalties in different patients. They have thus sought to define subgroups to improve research and treatment outcomes by focusing on a single subgroup at a time.
The genetic research which has been in the news was carried out by Dr. Jonathan Kerr and colleagues could well provide the basis for accurate subgrouping. The study found seven distinct types of ME/CFS based on variations in 88 genes and the proteins which they control. The types are as follows:
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.
I'm sure if you suffer from ME/CFS like I do this is quite exciting news and your initial reaction is to try to figure out which type you might have. It soon becomes obvious that this isn't exactly an easy task! In my case I seem to have characteristics from across the types but don't fit into a single types very well. I certainly don't have the most severe form of fatigue that leaves some patients unable to get out of bed and I don't suffer badly with the type of severe muscle and joint pain characteristic of fibromyalgia. I do experience severe depression, anxiety, sleep disturbances, gut problems, headaches and post-exertional fatigue.
So, although this is great news and undoubtedly furthers our understanding of the disease it doesn't provide us patients with any practical benefit just yet. We'll have to wait for further research to see if blood tests can be developed to look for levels of the proteins which these 88 genes code for. We'll then have a diagnostic test to determine which type we suffer from. From there let's hope that specific treatments can be developed.
How do you feel about the types of ME/CFS outlined by this research? Do you seem to match any of them? Let us know below!