Complement neoantigen and vitronectin are components of plaques in amyloid AL neuropathy.

We studied three patients with late onset, chronic sensorimotor and autonomic neuropathy in course of plasma cell dyscrasia with Bence Jones proteinuria. Histopathological findings of nerve biopsies consisted in diffuse loss of myelinated and unmyelinated fibers associated with perivascular deposits of amorphous material with physico-chemical and ultrastructural features of amyloid. By immunohistochemistry, light chains of the same type as Bence Jones protein, components of the classic and lytic pathways of the complement and vitronectin were detected at the level of amyloid nodules. The colocalization of complement neoantigen and vitronectin suggests that this complex derives from the circulation. The elucidation of the chemical composition of amyloid might shed some light in the pathogenesis of these disorders.