Lymphocytes in sural nerve biopsies from patients with plasma cell dyscrasia and polyneuropathy.

Sural nerve biopsies were examined in 36 patients with plasmacell dyscrasia and polyneuropathy. The M-component isotype was IgM in 19, IgG in 16 (one patient had both IgM and IgG) and IgA in 2 patients. Five of the IgM patients had Waldenström's disease, one of the IgG cases a myeloma and two lymphoma. The remaining 28 patients had monoclonal gammopathy of uncertain significance (MGUS). Nerve conduction studies showed signs of mixed axonal/demyelinating polyneuropathy in most cases. The biopsies were evaluated with regard to nerve fibre loss, segmental demyelination and inflammatory cell infiltration. Inflammatory cells infiltrating the nerves were found in 7 of 19 IgM cases and in 6 of 16 IgG cases. Immunohistochemical staining with monoclonal antibodies to B-lymphocytes and to subsets of T-lymphocytes was performed in 33 cases. An equal distribution of CD4 and CD8 positive T cells, but no B cells, were found among the inflammatory cells. The findings indicate a possible role for cell mediated immunological mechanisms in some patients with plasma cell dyscrasia associated with polyneuropathy.