[Chronic fatigue syndrome does exist. Changes of biological parameters are measurable]

Chronic fatigue syndrome is a debilitating condition characterised by neurocognitive and somatic symptoms. Although many patients report an infectious onset, there is no unequivocal evidence to support this. The immune system is activated, and the hypothalamic-pituitary-adrenal axis is involved. The aetiology is complex, and its understanding may require modification of our views on ill-health and disease.