Intravital video-capillaroscopy for the study of the microcirculation in psoriasis.

Intravital capillaroscopy using a video-microscopy system permits real-time imaging of the skin microvasculature with retrospective analysis of capillary dynamics. The addition of fluorescein angiography improves contrast and detects aspects of blood vessel behaviour, such as perfusion homogeneity and transcapillary solute diffusion, not detectable under native conditions. This study was performed to evaluate whether the method can be applied to the investigation of a skin disease and in particular the understanding of the role of the blood vessel in the pathogenesis of psoriasis. Results demonstrated clear differences between normal and psoriatic skin. More capillaries were red-cell perfused in both plaque and uninvolved skin compared to normal skin (P less than 0.001) and 0.01 less than P less than 0.02, respectively). The capillaries in psoriatic plaque skin were much larger than those in normal skin (P less than 0.001). The density of capillaries was not increased in plaque or uninvolved psoriatic skin, indicating expansion of existing vessels and not new vessel formation. The area of fluorescence seen around each capillary at 60 s was greater in plaque (P less than 0.001) and in uninvolved psoriatic skin (P less than 0.001) than in normal skin, indicating greater vessel transcapillary diffusion. This study confirms the value of video-microscopy as a non-invasive technique for the examination of the cutaneous microcirculation in vivo.