Table 2 Belgian (University Hospitals Leuven) diagnostic criteria for ‘habitual hyperthermia’ in 1990

1. Age 16 to 40 years with no immunosuppression or drug dependence

2. Axillary temperature less than or equal to 101.3°F (38.5 °C)

3. Increased body temperature after mild exertion

4. No effect of antipyretics

5. Additional functional symptoms include fatigue

6. No localising signs

7. No laboratory abnormalities (i.e. CBC w/diff, ESR, APP, s-TSH, ANA, urinalysis)

8. Normal chest X-ray and abdominal ultrasound

9. No alternative hypotheses