Characterization of amyloid deposits in biopsies of 15 with "sporadic" (non-familial or plasma cell dyscrasia amyloid polyneuropathy.

Review of the clinical and laboratory findings of 39 patients with amyloid polyneuropathy (AP) showed 12 cases to be hereditary and 12 to be associated with plasma cell dyscrasia (PCD). The remaining 15, termed "sporadic" AP, had neuropathy clinically indistinguishable from the other two groups but without a clinicopathologically identified PCD or positive family history. In an attempt to identify the type of amyloid in "sporadic" AP, the immunoreactivity of amyloid deposits was investigated using specific antisera raised against the following different chemical types of amyloid fibril proteins: variable regions of amyloid light chains kappa (A kappa) and lambda (A lambda), amyloid protein AA, and prealbumin. It was found that the amyloid in "sporadic" AP had A lambda antigenic determinants in ten cases, A kappa in one and prealbumin in three; in one case, the A lambda nature of amyloid was confirmed biochemically on the extracted amyloid fibrills. Thus, the most common type of AP in our population appears to be the "sporadic" form. In "sporadic" AP, the amyloid is most commonly of immunoglobulin light chain origin, even in the absence of overt PCD, and it can be rapidly categorized immunocytochemically to determine therapeutic directions or provide genetic guidance.