Amyloidogenic transthyretin Val30Met homozygote showing unusually early-onset familial amyloid polyneuropathy.

We report an amyloidogenic transthyretin (ATTR) Val30Met homozygote showing extremely early-onset, severe familial amyloid polyneuropathy (FAP). Although homozygotes have been reported to show late-onset and mild clinical manifestations, detailed analyses of the present and previously reported families suggest that homozygotes have a slightly more severe clinical course than heterozygotes. This is the youngest reported patient with ATTR Val30Met FAP, a condition believed to be attributable to homozygosity of this mutation. The clinical severity is consistent with TTR protein instability.