Evidence of immune deposits and of basement membrane alterations in dermal vessels of normal skin of patients with essential mixed cryoglobulinemia.

To gain insight into the pathogenic mechanisms of immune complex-mediated vasculitis, clinically normal skin specimens from the forearms of 12 patients with essential mixed cryoglobulinemia were investigated by light microscopy, immunofluorescence microscopy, and electron microscopy. Basement membrane alterations were documented in 9 patients. Eleven patients had deposits in vessel walls, but only in 1 was there evidence of inflammation. The same immunoglobulins of the cryoproteins could be demonstrated in the tissue deposits by immunofluorescence analysis and by immunoelectron microscopy. These findings suggest that, in essential mixed cryoglobulinemia, immune reactants in dermal vessels of normal skin are more common than is evidenced by clinical examination. Moreover, it seems that cryoglobulins, as such, are not sufficient to trigger an inflammatory process: Additional local or plasma factors are required. Deposits were absent in 7 patients with cryoglobulinemia that was associated with a primary disorder. This could be ascribed to the lower cryocrit levels documented in this group of patients, or to the shorter duration of their disease.