SCN9A and hereditary sensory and autonomic neuropathy: Multi-type bi-allelic pentanucleotide repeat expansion in RFC1 is the most common causative reason in our HSAN case series (25.3%), far ahead of the following genes, including WNK1/HSN2 (7.6%), NTRK1 (3.8%), SCN9A (3.8%), DNMT1 (2.5%), and NOTCH2NLC (1.3%).