Identification of a novel transthyretin Thr59Lys/Arg104His. A case of compound heterozygosity in a Chinese patient diagnosed with familial transthyretin amyloidosis.

Transthyretin (TTR) is a 127-amino acid residue protein synthesized mainly in the liver and in several minor sites, including the choroid plexus and the eye. In plasma, TTR circulates as a homotetramer and transports the hormone thyroxine and the retinol-binding protein-vitamin A complex. It is hypothesized that amino acid substitutions in TTR destabilize the tetramer by causing each subunit toform intermediates that may self-associate into amyloid fibrils.