Chronic fatigue syndrome
Chronic fatigue syndrome (CFS), also called myalgic encephalomyelitis (ME) and ME/CFS, is a complex, fatiguing, long-term medical condition diagnosed by required primary symptoms and criteria, and often involves a broad range of symptoms. Distinguishing core symptoms are lengthy exacerbations or "flares" of the illness after ordinary minor physical or mental activity, known as post-exertional malaise (PEM); greatly diminished capacity to accomplish tasks that were routine before the illness; and sleep disturbances. Orthostatic intolerance (difficulty sitting and standing upright) and cognitive dysfunction are also diagnostic. Other common symptoms may involve numerous body systems, and chronic pain is common.