Objective. To investigate the role of hepatitis C virus (HCV) in the pathogenesis of the cutaneous vasculitis in patients with type II cryoglobulinemia.

Methods. Using in situ hybridization detection of HCV, we studied 6 test patients and various control subjects. Serum HCV was quantitated, cryoglobulins were analyzed by column chromatography at 37°C, and lowdensity lipoprotein (LDL) receptors on keratinocytes were detected using LDL labeled with fluorescent dye.

Results. In the cutaneous vasculitic lesions from test patients, but not control subjects, the HCV virion was found in association with IgM and IgG. HCV alone was detected in some vessel walls, and in skin and ductal epithelium and vascular endothelium in inflamed, but not normal, skin. Cryoglobulins showed HCV, monomeric IgM, and monomeric IgG, with little or no immune complexes. The extent of the lesions correlated with levels of viremia. Up-regulation of LDL receptors on keratinocytes was detected in inflamed, but not normal, skin.

Conclusion. HCV was present in the cutaneous vasculitic lesions, most likely in complexes with IgM and IgG formed in situ. These findings and the correlation of the severity of the rash with the level of viremia suggest that HCV plays a major role in the pathogenesis of cutaneous vasculitis in these patients and strengthens the rationale for antiviral drug therapy. The presence of HCV in keratinocytes and ductal epithelial and vascular endothelial cells may be the in vivo manifestation of endocytosis of HCV by the LDL receptors that has recently been demonstrated in vitro. The upregulation of LDL receptors on keratinocytes in inflamed skin is consistent with this postulation.