Walsh & Hoyt: Pathology

Nerve biopsies show demyelination in 2040% of cases of CIDP. Onion-bulb formation occurs in 1040%, indicating repeated episodes of demyelination and remyelination. The material surrounding the nerve fibers is predominantly connective tissue. Mononuclear cell infiltrates occur in 2550% of biopsy specimens. In some pathology studies, there is little or no inflammation in the majority of specimens. Immunohistochemistry in 13 cases showed 10 with endoneurial infiltration of CD3+ T-cells. Epineural T cells were present in 11 of the 13 cases. Hypesthesia was associated with significantly higher numbers of macrophages. C3d and sometimes IgM have been demonstrated on the myelin sheaths of the sural nerves in CIDP. There may be concomitant axonal loss secondary to primary demyelination. Axonal loss is the major long-term poor prognostic indicator in CIDP.