Congenital analgesia
| Congenital insensitivity to pain | |
|---|---|
| Classification and external resources | |
| OMIM | 243000 147430 |
| DiseasesDB | 31214 |
| MeSH | D000699 |
Congenital insensitivity to pain (CIP), also known as congenital analgesia, is one or more rare conditions in which a person cannot feel (and has never felt) physical pain. The conditions described here are separate from the HSAN group of disorders, which have more specific signs and etiology. It is an extremely dangerous condition.
For people with this disorder, cognition and sensation are otherwise normal; for instance, patients can still feel discriminative touch (though not always temperature), and there are no detectable physical abnormalities.
Children with this condition often suffer oral cavity damage both in and around the oral cavity (such as having bitten off the tip of their tongue) or fractures to bones. Unnoticed infections and corneal damage due to foreign objects in the eye are also seen. Because the child cannot feel pain, they may not respond to problems, thus being at a higher risk of more severe diseases.
There are generally two types of non-response exhibited:
In some cases, the condition is caused by increased production of endorphins in the brain, in which case naloxone may be a treatment, but does not always work. In all cases, this disorder can be in the voltage-gated sodium channel SCN9A (Nav1.7). Patients with such mutations are congenitally insensitive to pain and lack other neuropathies. There are three mutations in SCN9A: W897X, located in the P-loop of domain 2; I767X, located in the S2 segment of domain 2; and S459X, located in the linker region between domains 1 and 2. This results in a truncated non-functional protein. Nav1.7 channels are expressed at high levels in nociceptive neurons of the dorsal root ganglia. As these channels are likely involved in the formation and propagation of action potentials in such neurons, it is expected that a loss of function mutation in SCN9A leads to abolished nociceptive pain propagation.
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