Dual wavelength (532 and 633 nm) laser Doppler imaging of plaque psoriasis

Background: Increased blood flow occurs in plaques of psoriasis, and an increase in blood flow has been shown to occur in uninvolved skin adjacent to the active edge. Objectives: In order to gain more insight into the pathophysiology of the active edges of plaques of psoriasis, we investigated different components of the microcirculation in the lesional and nonlesional skin of patients with psoriasis, using dual wavelength laser Doppler imaging (LDI). Methods: The cutaneous blood flow in 23 plaques on the forearms of 20 patients with chronic plaque psoriasis was recorded using dual wavelength LDI. Perfusion was determined within the plaque (P), in uninvolved skin adjacent to the plaque (A) and in nonadjacent skin (U). Results: Perfusion in plaques was increased as imaged by either 633 nm (red wavelength) or 532 nm (green wavelength) compared with both adjacent and nonadjacent uninvolved skin: median (interquartile range) P/ARED = 3.7 (2.5-4.9), P/AGREEN = 1.3 (1.2-1.6), P/URED = 4.2 (2.7-6.1), P/UGREEN = 1.5 (1.3-1.9). Conclusions: Vascular perfusion is increased within plaques of psoriasis compared with adjacent and nonadjacent uninvolved skin. The results suggest an area of increased perfusion in skin adjacent to plaques, when compared with nonadjacent skin, for both deeper (large) and superficial (small) vessels (imaged by 633 and 532 nm, respectively). We believe that this dual wavelength tool may be a suitable and useful way of assessing pathophysiology and treatment response in psoriasis. © 2005 British Association of Dermatologists.