Null Mutation in SCN9A in which noxious stimuli can be detected in the absence of pain
Ramirez JD., Habib AM., Cox JJ., Themistocleous AC., McMahon SB., Wood JN., Bennett DLH.
The term nociception was originally defined by Sherrington1 as the neural process by which high-threshold stimuli (which cause tissue injury) are detected. This is distinct from pain, which is defined by the quality of the sensory percept (i.e., unpleasant), is not always evoked by a noxious stimulus, and can also be experienced in the absence of a noxious stimulus. In man, recessive loss of function mutations in the SCN9A gene, encoding the α subunit of Nav1.7, results in anosmia and the congenital inability to experience pain,2–4 but there have been few reports of detailed sensory testing in these patients.