Biochemical nature of familial amyloiditic polyneuropathy and a new diagnostic method by radioimmunoassay

Familial amyloidotic polyneuropathy (FAP) in Japan is clinically similar to that of Portugal. We have reported that amyloid fibril protein isolated from Japanese FAP cases is composed of a prealbumin variant in which a valine residue at position 30 is replaced by a methionine (Tawara et al., 1983). Furthermore, we have clarified that this prealbumin variant is present in the sera of Japanese FAP patients. There has been no definite method to detect this progressive illness before clinical manifestations appear. For the purpose of developing a new, noninvasive diagnostic method, we have established a radioimmunoassay (RIA) using a nonapeptide corresponding to the subsequence (22-30) of the prealbumin variant. The serum levels of the prealbumin variant in normal individuals, FAP patients, asymptomatic members of FAP families, primary and secondary amyloidosis cases are studied. The present RIA serves as a simple and definite method for an early detection of this disease and an appropriate genetic advice can be given to FAP patients and their families