Loss-of-function mutations in the Nav1.7 gene underlie congenital indifference to pain in multiple human populations.

Congenital indifference to pain (CIP) is a rare condition in which patients have severely impaired pain perception, but are otherwise essentially normal. We identified and collected DNA from individuals from nine families of seven different nationalities in which the affected individuals meet the diagnostic criteria for CIP. Using homozygosity mapping and haplotype sharing methods, we narrowed the CIP locus to chromosome 2q24-q31, a region known to contain a cluster of voltage-gated sodium channel genes. From these prioritized candidate sodium channels, we identified 10 mutations in the SCN9A gene encoding the sodium channel protein Nav1.7. The mutations completely co-segregated with the disease phenotype, and nine of these SCN9A mutations resulted in truncation and loss-of-function of the Nav1.7 channel. These genetic data further support the evidence that Nav1.7 plays an essential role in mediating pain in humans, and that SCN9A mutations identified in multiple different populations underlie CIP.

A report of congenital indifference to pain as diagnosed in infancy.

As physicians and nurses, we have a fundamental obligation to consider patient welfare above all else. The case presented demonstrates the depth of this obligation. Our patient, who was diagnosed during infancy with congenital indifference to pain, can neither feel nor perceive the meaning of pain. Congenital indifference to pain is a rare disorder, which is characterized by normal intelligence, development, and sensation despite an absence of pain perception. There is no cure and treatment difficulties are plentiful. Educating and maintaining an open, consistent relationship with the family and caregivers is essential to reduce the morbidity of this condition.