Reticulate purpura, cryoglobulinaemia and livedo reticularis.

Two patients with type I cryoglobulinaemia are described, both of whom presented with purpura in a reticulate distribution on the legs, resembling the pattern of physiological livedo. It appeared that increased cooling due to sluggish blood flow in areas of the skin corresponding to the blue areas of physiological livedo may have caused the localization of cryoprecipitate at these sites. To investigate the pathogenesis of the net-like pattern of purpura, three subjects with physiological livedo reticularis of the thighs were studied with a laser-Doppler velocimeter. In two subjects, mean blood flux in the blue areas was 21% (P < 0.01) and 26% (P < 0.02) lower than in adjacent white areas, whereas in the third there was no significant difference. The cutaneous features of cryoglobulinaemia, and the mechanism of the reticulate purpura in this condition, are discussed.