Consideration of narcolepsy in the differential diagnosis of chronic fatigue syndrome.

OBJECTIVE

To justify the inclusion of narcolepsy in the differential diagnosis of patients with chronic fatigue.

CLINICAL FEATURES: We report three patients aged 17 (two women and one man) and one woman aged 45 who had been diagnosed as having chronic fatigue syndrome (CFS). They had no psychiatric illness. Their main problem was severe daytime sleepiness, presenting as "tiredness and fatigue". The history, sleep study and multiple sleep latency test suggested a diagnosis of narcolepsy.

INTERVENTION: Treatment with methylphenidate resulted in complete resolution of symptoms in two patients and significant improvement in the other two.

CONCLUSIONS

The differential diagnosis of CFS requires the exclusion of other conditions. If daytime sleepiness is a major complaint, other symptoms of narcolepsy should be sought and the diagnosis confirmed with sleep study and a multiple sleep latency test.