A novel variant mutation of transthyretin Ile73Val-related amyloidotic polyneuropathy in Taiwanese

Familial amyloidotic polyneuropathy (FAP) is an inherited disease caused by deposition of mutant amyloid proteins in the peripheral nerves. Abnormal transthyretin (TTR) accounts for protein aggregation in the majority of FAP. Val30Met is the most common TTR gene-mutation reported in different ethnic populations. In Taiwan, Ala97Ser mutation is probably a major hot-spot of TTR mutations. On the other hand, Ile73Val mutation was only reported in one Bangladeshi family. We reported here the first patient of amyloidotic polyneuropathy with Ile73Val TTR mutation in Taiwan.

This patient had symptoms and signs of sensory motor polyneuropathy and early gastrointestinal autonomic dysfunction since around 50 years old. A nerve conduction velocity (NCV) study showed typical axonal sensory-motor polyneuropathy. A standard autonomic function test revealed orthostatic hypotension and was compatible with cardiovascular autonomic dysfunction. There was also impaired sudomotor activity. An echocardiogram study suggested amyloidotic restrictive cardiomyopathy. A genetic analysis revealed Ile73Val TTRR mutation.

We reported the first patient with Ile73Val TTR mutation in Taiwan, who had earlier gastrointestinal dysfunction. Similar to the Bangladeshi patient reported in the previous article, painful neuropathy, a feature typically presented in more common TTR gene mutations, is absent.