Identification of carriers of mutant prealbumin gene associated with familial amyloidotic polyneuropathy type I by Southern blot procedures: study of six pedigrees in the Arao district of Japan.

Fifty-six Japanese individuals from six pedigrees with familial amyloidotic polyneuropathy (FAP), together with 2 individuals with symptomatic FAP from an unknown pedigree were analyzed, using the Southern blot procedures for the prealbumin gene structure. A human prealbumin cDNA was used as the probe. Altogether, these individuals included 20 with symptomatic FAP, 30 who were asymptomatic, and 8 disease-free spouses. Twenty individuals with symptomatic FAP were all heterozygous for the prealbumin genes, carrying one normal and one mutant gene. We confirmed the direct linkage between the mutant prealbumin gene and the Japanese type of FAP. Moreover, 10 of the 30 asymptomatic individuals from pedigrees with FAP were also heterozygous for the prealbumin gene. The number of asymptomatic individuals with the mutant prealbumin gene showed age-related decreases, and none was over 40 years. A linkage between the mutant prealbumin gene and serum levels of the prealbumin variant was also evident.