The 7 Genomic Subtypes of Chronic Fatigue Syndrome

The first diagnostic test for chronic fatigue syndrome (CFS or ME/CFS) could be on its way, thanks to a genomics study lead by Jonathan R. Kerr, MD, Ph.D., of St. George's University in London. Researchers discovered and defined seven genomic subtypes of ME/CFS based on 88 genes that are expressed differently in people with the condition. The study was published in the December 2007 issue of the Journal of Clinical Pathology.

When blood from people with ME/CFS was compared to that from healthy donors, researchers were able to figure out that in each case, certain genes from that group of 88 were producing different levels of proteins and other molecules, how these genes interacted with other genes, their disease associations and their affects on molecular and cellular function.

Many ME/CFS researchers believe this research is crucial for devising better diagnostic criteria and treatments. Also, finding concrete genomic differences between people with ME/CFS and healthy people is one more piece of biological evidence that ME/CFS is not a psychiatric condition but a physiological one. This could help eliminate the stigma and skepticism often faced by people with the condition.

The 7 Subtypes of Chronic Fatigue Syndrome

The genetic differences in subtypes correlates with clusters of symptoms and also with how severe they are. The most severe cases involve up to 71 of the possible 88 gene abnormalities and include anxiety/depression. Because the genomic analysis was performed on people diagnosed with ME/CFS, they all had persistent fatigue. Therefore, all of the subtypes include fatigue.

The 7 subtypes are:

• Subtype 1
  This is one of the more severe subtypes. Effects are cognitive, musculoskeletal, sleep-related and anxiety/depression.
• Subtype 2
  This is one of the more severe subtypes. Effects are musculoskeletal, pain and anxiety/depression.
• Subtype 3
  This subtype has the mildest symptoms.
• Subtype 4
  This subtype is dominated by cognitive issues.
• Subtype 5
  Effects are musculoskeletal and gastrointestinal.
• Subtype 6
  This subtype is dominated by post-exertional malaise (extreme crash after exercise or exertion.)
• Subtype 7
  This is one of the more severe subtypes. Effects are pain, infections, musculoskeletal, sleep-related, neurological, gastrointestinal, neurocognitive and anxiety/depression.

Dr. Kerr emphasizes that each subtype is a distinct condition. This is the first study to identify these genomic subtypes and it will need to be verified by more research before the information is put to use in diagnosing or treating people with the disorder.

Other findings:

• Many of the abnormal genes are ones that researchers know can be affected by viral infections, which they believe are a predominant trigger of many ME/CFS cases.
• Drugs that are already on the market for other diseases target five of the 88 genetic abnormalities, meaning potential treatments for some subtypes may already be available.
• The team is now looking into whether the abnormal protein levels are detectable in the blood, meaning they'd be considered biological indicators of ME/CFS and could be used for diagnostic tests.