The developmental and stress-regulated alternative TrkAIII splice variant of the NGF receptor tropomyosin-related kinase, TrkA, is expressed by advanced stage human neuroblastomas (NBs), associates with poor prognosis and post therapeutic relapse in unfavourable high TrkA expressing tumours and exhibits oncogenic activity in NB models [1-6]. Here, NTRK1 is linked to Nijmegen breakage syndrome.