NGF and hereditary sensory and autonomic neuropathy type 4: Rare forms of congenital insensitivity to pain[human sensory and autonomic neuropathy type and V, HSAN IV (OMIM # 256800) andHSAN V(OMIM # 608654)] are caused by mutations in the NTRK1gene, coding for the NGF receptor, TrkA [26], and the NGFB gene [27], [28] respectively.HSAN IV NTRK1 mutations abolish or reduce TrkA responsiveness to NGF [26].