In the cases of HSAN IV (OMIM # 256800) (Indo et al., 2001; Indo, 2002) and HSAN V (OMIM # 608654) (Einarsdottir et al., 2004; Minde et al., 2004), which are caused by mutations in the genes coding for the TrkA and NGF respectively, both of them are all involved in NGF signaling pathway abnormality. This evidence concerns the gene NTRK1 and hereditary sensory and autonomic neuropathy type 5.