Chronic fatigue syndrome criteria in patients with other forms of unexplained chronic fatigue.

To determine the prevalence of chronic fatigue syndrome (CFS) criteria in other forms of unexplained chronic fatigue, 297 consecutive outpatients under the age of 40 from a general medicine practice were studied. After excluding the three with chronic fatigue syndrome, the remaining 294 individuals were divided into those with unexplained chronic fatigue (64 patients) those without (the remaining 230 patients). Chronic fatigue syndrome criteria noted to be significantly more common in those with unexplained fatigue compared to those without include: fever, painful adenopathy, muscle weakness, myalgia, headache, migratory arthralgia, neuropsychologic symptoms, and sleep disorder. Like chronic fatigue syndrome, unexplained chronic fatigue often started suddenly. I conclude that the CFS criteria are noted more commonly than expected in other forms of unexplained chronic fatigue.