NTRK2 and obesity due to melanocortin 4 receptor deficiency: A rare de novo missense variant in BDNF and seven NTRK2 mutations along with three variants previously reported [23] have also been functionally characterized by Sonoyama et al. Clinical data collected from carriers of BDNF/TrkB variants showed in addition to severe obesity, a spectrum of neurobehavioral disorders such as hyperactivity, learning deficit and shot-term memory impairment [29].