Polyneuropathy as an initial manifestation of Hereditary Transtyretin Amyloidosis (ATTRV) in a young patient: Case report of a diagnostic challenge.

We report the case of a 27-year-old man with transthyretin amyloidosis secondary to the p.Val142Ile mutation with an atypical clinical presentation of predominantly lower limb polyneuropathy without cardiac involvement. p.Val142Ile is mainly associated with cardiopathy, whereas the neuropathic phenotype is mainly associated with p.Val50Met. Our patient belongs to a non-endemic region and due to his lack of support network a possible familial component is unknown. His case represents a diagnostic challenge given the wide heterogeneity of clinical manifestations associated with the disease, with other possible diagnoses of polyneuropathy being reasonably excluded according to prevalence and frequency. The particularly unusual genotype-phenotype association distinguishes this case from the classic description of transthyretin amyloidosis secondary to p.Val142Ile.