Congenital Indifference to Pain is a unique disorder characterized by absence of pain perception from birth, universal lack of response to noxious stimuli, normal sensitivity to other modalities, normal myotactic responses and normal mental development. The first description of this condition appeared in 1931; the affected individual is popularly known as the "human pincushion". Patients with Congenital Indifference to Pain generally present with repeated trauma, fractures or self mutilation. They lack the normal defensive response to pain sensation but the response to other sensations is normal. The criteria for the diagnosis of congenital indifference to pain are not well defined, probably due to lack of recent investigative facilities in the past. 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.
Congenital Indifference to Pain is caused by mutations in the SCN9A (Sodium Channel, Voltage-Gated, Type IX, Alpha Subunit) gene. This gene encodes a voltage-gated sodium channel, which plays a significant role in nociception signaling. Mutations in this gene have been associated with primary erythermalgia, channelopathy-associated insensitivity to pain, and paroxysmal extreme pain disorder. In cells expressing mutant protein, the currents are no greater than background; this is indicative that SCN9A is an essential and nonredundant requirement for nociception in humans.
