Fatigue of unknown aetiology--a review.

The patient complaining of fatigue presents the physician with the dilemma of distinguishing a psychological disorder from a physical illness in its early stage. Information relating this nonspecific complaint to specific diagnoses is scarce. Consequently, laboratory investigation of fatigue has been empirical. Five separate reports of patients with fatigue (n = 940) are reviewed. 'Psychologic' causes accounted for 57% of cases. Of the 36.7% of cases with 'physical' causes, infection represented the largest group followed by cardiovascular and endocrine abnormalities. In these reports, the cases of cancer and connective tissue disease was remarkably few (1% each). Duration of fatigue and patient age may be important clues to the underlying diagnosis. Appropriate laboratory investigations and suitable areas for future research are suggested.