Peripheral neuropathy with essential mixed cryoglobulinemia: biopsies from 5 cases.

Essential mixed cryoglobulinemia, which can cause hypersensitivity vasculitis, was observed in five patients with peripheral neuropathy. Three cases presented with multifocal neuropathies and two cases with symmetrical polyneuropathy. One had cryoglobulinemia with IgM monoclonal gammopathy IgG polyclonal gammopathy, and the other four had cryoglobulinemia with polyclonal gammopathy. Biopsies showed perivascular infiltration by mononuclear cells around medium, and mainly small-sized blood vessels. This was observed in the epineurium (five cases) and muscular fragments (three cases). At ultrastructural examination two cases showed severe damage of most myelinated fibers, which presented acute stages of Wallerian-like degeneration, and the three other cases showed a less widespread destruction of myelinated fibers. Most endoneurial capillaries showed swollen endoneurial cells. Myelino-axonal degeneration of myelinated fibers is probably due mainly to the vasculitis always present in the epineurium. This damage was probably worsened by the modifications of endoneurial capillaries. These lesions and their mechanisms are quite different from those observed in cases of cryoglobulinemia with an isolated monoclonal gammopathy.