Null mutation in SCN9A in which noxious stimuli can be detected in the absence of pain

may be due to an intact blood–brain barrier (BBB), which restricts entry of serum IgG into the CNS. It has recently been reported that AQP4-IgG can be present in serum several years before clinical onset of NMO. 7 In addition, experimental studies have shown induction of NMO-like histopathology by transfer of human AQP4-IgG to animals only provided BBB breakdown. 2 Further studies are needed to evaluate the neuro-logic outcome of infants and children of mothers with NMO given the evidence that AQP4-IgG can be passively transferred to the fetus. report no disclosures relevant to the manuscript. B. Weinshenker has received a research grant from the Guthy Jackson Foundation. He receives royalties from RSR for a technology license related to a test for aquaporin-4 autoantibodies for diagnosis of neuromyelitis optica. He serves on data safety monitoring committees for Novartis, Biogen-Idec, and Mitsubishi pharmaceutical companies, and serves on an adjudication panel for Medimmune Pharmaceuticals. He served as a consultant for optica and pregnancy during therapeutic B cell depletion: infant exposure to anti-AQP4 antibody and prevention of rebound relapses with low-dose rituximab postpartum. A case of NMO sero-positive for aquaporin-4 antibody more than 10 years before onset. The term nociception was originally defined by Sher-rington 1 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 a subunit of Na v 1.7, 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. Case report. A 27-year-old man who participated in the Painful Channelopathies Study (NRES-UK reference: 12/LO/0017) had a history of self-mutilating behavior during childhood and multiple painless injuries with normal cognitive development. He had never perceived pain but reported that otherwise somatosensation was normal. In his late teens, he learned to avoid injury by attending to what he described as a tingling sensation, which was not unpleasant but that he noted only occurred in the context of threatened tissue injury. The family pedigree is shown in the figure, A. He had 2 sisters, one of whom died in childhood as a consequence of sepsis. …