[Clinicopathological features of familial amyloid polyneuropathy]

Because of the recent development of biochemical and molecular analyses, familial amyloid polyneuropathy (FAP) is not considered to be rare as previously thought. Transthyretin Val30Met-associated FAP (FAP ATTR Val30Met) is a most common form of FAP. Although patients with FAP ATTR Val30Met have been considered to be concentrated in endemic foci of Japan, Portugal, and Sweden, late-onset form of this type of FAP was discovered in non-endemic areas and they revealed to be distributed widely throughout the world. Therefore, the necessity for recognition of the variability in clinical, electrophysiological, and histopathological features of this disease become increasing. In this article, we describe clinicopathological features of FAP ATTR Val30Met patients in Japan by comparing those of conventional early-onset cases from endemic foci to those of late-onset ones from non-endemic areas. Patients with FAP ATTR Val30Met from endemic foci and those from non-endemic areas show different clinical, electrophysiological, and histopathological features. As compared to a classic phenotype of FAP, clinicopathological features of patients from non-endemic areas tend to be nonspecific. Physicians may not take the possibility of FAP into consideration until amyloid became evident by sural nerve biopsy. Therefore, tight recognition for the possibility of FAP ATTR Val30Met are needed at the time of initial evaluation of neuropathy of undetermined etiology to avoid missed diagnosis.