There are many answers possible for this vague question, however, you may be thinking of fibromyalgia.
Fibromyalgia syndrome
Chronic fatigue syndrome
Chronic Fatigue Syndrome is a disorder, or collection of symptoms, primarily characterized by extreme fatigue that persists for a period of at least six months. Other symptoms may include chronic pain, headaches, and IBS.
chronic fatigue syndrome
Fibryomyalgia or polymyalgia.
Because the cause of CFS is not known, there are no recommendations for preventing the disorder.
Because the cause of CFS is not known, there currently are no recommendations for preventing the disorder
Pathological fatigue refers to extreme and persistent tiredness that is not alleviated by rest. It can be a symptom of various medical conditions, such as chronic fatigue syndrome, multiple sclerosis, or fibromyalgia. It significantly impacts daily functioning and quality of life.
It has been called chronic fatigue and immune disorder (CFIDS), myalgic encephalomyelitis, low natural killer cell disease, post-viral syndrome, Epstein-Barr disease, and Yuppie flu
Chronic fatigue syndrome
Mostly, immunologists (physicians interested in the immune system) have studied Chronic Fatigue Syndrome.
Stephen E. Straus has written: 'Chronic fatigue syndrome' -- subject(s): Chronic fatigue syndrome