Familial amyloidotic polyneuropathy (FAP), now more commonly known asvariant transthyretin amyloidosis(ATTRv), encompassing polyneuropathy (ATTRv-PN) and cardiomyopathy (ATTRv-CM), is a progressive and life-threatening disorder caused by mutations in thetransthyretin(TTR) gene. This evidence concerns the gene TTR and cutaneous mastocytosis.