Thermosensory abnormalities and blood flow dysfunction in psoriatic skin.

BACKGROUND: Accumulating data have shown evidence of involvement of cutaneous nerve fibres and neuropeptides in psoriasis. Although ample evidence of structural and biochemical data exist no studies have been done on assessing the function of small nerve fibres in this disease.

OBJECTIVES: To investigate the function of small nerve fibres in patients with psoriasis between psoriatic plaques and non-involved skin and in comparison with healthy controls.

METHODS: We performed computerized psychophysical thermal sensory testing of warmth, cold and heat pain thresholds and skin blood flow using laser Doppler imaging in psoriatic lesions vs. non-involved skin and healthy skin. We evaluated these parameters before and immediately after barrier perturbation, and 1 week after as a measure of barrier repair.

RESULTS: There is a significantly elevated warm and decreased cold sensation threshold in psoriatic skin compared with non-involved skin and skin of healthy controls in the same sites. These differences were particularly abnormal 1 week poststripping. The warm sensation threshold was significantly elevated in non-involved skin in psoriatics vs. skin of healthy controls after tape stripping. These findings suggest there is an abnormal function of cutaneous nerve fibres in response to trauma to the stratum corneum, which is not limited to the visible plaque but could be generalized and aggravated by stressful events. Skin blood flow was significantly elevated in psoriatic plaques and inversely correlated to warm sensation thresholds while in healthy controls a direct correlation was noted.

CONCLUSIONS: Our data demonstrate an abnormal thermosensory response in psoriasis.