Are psoriatic patients at risk of heat intolerance?

Sixteen young male subjects with psoriasis (mean of 4.9% of skin surface area involvement) and 10 healthy controls underwent a heat exercise test (40 °C, 40% r.h.) for 2 h. Rectal temperature (Tr). mean skin temperature (Tsk), heart rate (HR) and heat storage (dS) were measured and calculated. A sharper rise was found for all parameters in the psoriatic patients as compared with controls. Statistically significant differences were found in Tr after 60 min (37.9 ± 0.1°C and 37.5 ± 0.1°C in patients and controls, respectively) and at termination of the exercise (38.3 ± 0.1°C and 37.5 ± 0.1°C). Heat storage at the end of the first hour was 78 ± 9 and 30 ± 7 kcal in patients and controls, respectively. At the end of 120 min. heat storage in the study group increased to 87 ± 14 kcal. while the control group stored only 30 ± 7 kcal. Sweat rate was lower in the psoriatic patients (590 ± 49 g/h) than in controls (691 ± 42 g/h). even when corrected for healthy skin area (337 ± 26 g/h/m2 compared with 370 ± 24 g/h/m²). It is suggested that psoriatic patients have a reduced ability to dissipate extra heat during exposure to exercise in the heat. Psoriasis should therefore be considered as a risk factor for heat intolerance.