Congenital insensitivity to pain with anhidrosis

Congenital insensitivity to pain with anhidrosis (CIPA) is an extremely rare inherited disorder of the nervous system which prevents the sensation of pain, heat, cold, or any real nerve-related sensations (including feeling the need to urinate); however, patients can still feel pressure. CIPA is the fourth type of hereditary sensory and autonomic neuropathy (HSAN), known as HSAN IV. (It is also referred to as HSAN Type IV). A person with CIPA cannot feel pain or differentiate even extreme temperatures. "Anhidrosis" means the body does not sweat, and "congenital" means that the condition is present from birth.

Clinical description
Patients with this disorder are very likely to injure themselves in ways that would normally be prevented by feeling pain. The main features of the disorder are lack of pain sensation, painless injuries of the arms, legs and oral structures, hyperthermia during hot weather because of inability to sweat, mental retardation as a result of hyperthermia, infection and scarring of the tongue, lips and gums, chronic infections of bones and joints, bone fractures, multiple scars, osteomyelitis and joint deformities, which may lead to amputation. Other common problems include eye related ones, such as infection due to the sufferers rubbing them too hard, too frequently or scratching them during sleep.

Differential diagnosis
Congenital insensitivity to pain with anhidrosis may be misdiagnosed for leprosy, based on similar symptoms of severe injuries to the hands and feet.

Cause
CIPA is caused by a genetic mutation which prevents the formation of nerve cells which are responsible for transmitting signals of pain, heat, and cold to the brain. Overheating kills more than half of all children with CIPA before age 3.

The genetic mutation is in the gene encoding the neurotrophic tyrosine kinase receptor (NTRK1 gene).

Treatment
Treatments for CIPA do not always work; however, there are some cases where naloxone may be used as a treatment. Naloxone is a chemical that acts within the nervous system of the body by blocking the nervous system from causing the inactions that occur within the group of cells that receives the message to initiate the sensation of pain, heat, or cold. Most treatments are hard to narrow down for this condition because each CIPA patient may have other conditions including the absence of a sweat gland, nerve fibers, ulcers, and other sub-conditions. It has been suggested that young CIPA sufferers have their baby teeth removed so they cannot chew through their tongue, lips or fingers until their full set of adult teeth grow through.

Incidence
CIPA is extremely rare. There are 84 documented living cases in the United States; there are more than 300 in Japan. Only one case is documented in New Zealand, while two cases have been documented in Morocco. Sixty cases had been reported worldwide by 1983, when CIPA was first listed as a disorder.

Most infants afflicted with the disorder do not live past 3 years of age, and those who do rarely pass age 25. The reason for the short life span is often related to the sufferer's inability to sweat, which leads to hyperthermia, to which infants are especially susceptible. Vital signs need to be monitored closely since patients are generally unable to feel when something is wrong.

In the media
In the third season of the TV series House in the episode "Insensitive" (14th episode), the patient (Hannah Morganthal, played by Mika Boorem) suffers from this condition.

In the third season of the TV series Grey's Anatomy in the episode "Sometimes a Fantasy", Abigail Breslin's character, Megan Clover, is diagnosed with this condition.

Baby Carson was featured on Discovery Health Channel's Mystery Diagnosis episode "The Boy Who Never Cried", which aired on 21 November 2009. Dr. David Christopher of Valley Children's Clinic, Renton, Washington is his doctor.

In Stieg Larsson's novel The Girl Who Played with Fire, one of the villains, known through most of the book as the "blonde giant", suffers from the disorder.

In the 2010 film Bereavement, 6 year old Martin Bristol, one of the main characters, suffers from CIPA.