A protein-tyrosine kinase receptor that is specific for NERVE GROWTH FACTOR; NEUROTROPHIN 3; neurotrophin 4, neurotrophin 5. It plays a crucial role in pain sensation and thermoregulation in humans. Gene mutations that cause loss of receptor function are associated with congenital insensitivity to pain with anhidrosis, while gene rearrangements that activate the protein-tyrosine kinase function are associated with tumorigenesis.