Here is a medically acceptable description of this illness:
Chronic fatigue syndrome (CFS), also known as chronic fatigue and immune dysfunction syndrome (CFIDS), myalgic encephalomyelitis (ME) and by other names, is a complex and debilitating chronic illness that affects the brain and multiple body systems.
CFS is characterized by incapacitating fatigue (experienced as profound exhaustion and extremely poor stamina) and problems with concentration and short-term memory. It is also accompanied by flu-like symptoms such as pain in the joints and muscles, un-refreshing sleep, tender lymph nodes, sore throat and headache. A distinctive characteristic of the illness is post-exertional malaise, a worsening of symptoms following physical or mental exertion occurring within 12-48 hours of the exertion and requiring an extended recovery period.
When I first received a proper diagnosis of this illness I was devastated. It sounded final and left me with little or