NTRK1 and hereditary sensory and autonomic neuropathy type 4: 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.