Aetiology
The precise cause(s) and pathogenic mechanism(s) are yet to be fully defined in
CFS/ME, however it is likely that the aetiology of CFS/ME is multifactorial in nature.
Environmental factors, abnormal physiological pathways and genetic pre-disposition
are all likely to contribute to symptom production and response to illness in
CFS/ME.
CFS/ME research studies have shown abnormalities in brain structure/function
(including neuroendocrine responses), muscular function, immune function and
sleep disturbance, along with associations with certain infectious factors. However,
these have remained isolated findings, which require further study and verification in
clinical trials.
The multiplicity of proposed causes such as an infectious disease (e.g. infectious
mononucleosis), altered stress hormone response, altered immune response,
altered gene expression, sleep problems, alterations of mood, coping strategies,
and toxin/chemical exposure give further weight to the argument that the composite
term CFS/ME best describes this condition currently and that it is a spectrum of
disease.
It is considered probable that several different conditions exist with different disease
mechanisms within the overall case definition. Much research is directed at trying to
identify these so called different ‘phenotypes’. This is because it is likely that
different phenotypes will require different therapeutic approaches.
Predisposing factors that have been identified include certain personality features
(introversion and neuroticism) [4] and inactivity in childhood. [5]
Twin studies have shown a familial predisposition, although no genetic defects have
been found so far. [6]
Precipitating factors include an infectious trigger in up to three quarters of patients.
[7] Many infective ‘triggers’ have been identified including Epstein-Barr virus (EBVthe
cause of infectious mononucleosis/glandular fever), hepatitis A, influenza and
coxsackie virus.
However, it has proved difficult to establish a causal link between CFS/ME and past
viral infection. There is currently no evidence that CFS is caused by any ongoing
chronic infection.
Other stressful life events (such as death of close family members or loss of a job)
or difficulties may be associated with the development of CFS/ME, particularly if the
stress is ongoing. [8] A combination of some adverse life event in combination with
a recent infection is a common scenario in clinical practice.