Chronic fatigue syndrome
Chronic fatigue syndrome (CFS), also called myalgic encephalomyelitis, is a complex long-term medical condition which often stops people from working or leading a normal life. The  disease is not fully understood.   Diagnosis is based on the person's symptoms, which usually include pain, because there is no agreed diagnostic test.  There is no agreed definition, but it may affect as many as 1% of the population in some places.