Congenital insensitivity to pain with anhidrosis

Congenital insensitivity to pain with anhidrosis (CIPA), also called hereditary sensory and autonomic neuropathy type IV — 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" indicates that the condition is present from birth.

Clinical description

Charcot joints are demonstrated in this boy with HSAN IV or congenital insensitivity to pain with anhidrosis (CIPA). The right knee and right ankle (on the left of the picture) are enlarged and distorted. The skin over the medial aspect of the ankle is darkened with a draining wound secondary to superimposed osteomyelitis. There are other areas of trauma and ulcers including a site on the right heel.

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, syndromic intellectual disability 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 are eye related, such as infection due to the sufferers rubbing them too hard, too frequently or scratching them during sleep. In addition, patients typically lack unmyelinated and small myelinated nerve fibers in the dorsal root ganglion. Both are responsible for transmitting pain signals. In addition, patients' sweat glands are normal in both structure and function, though they lack innervations by small diameter neurons.^[1]

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. The disorder is autosomal recessive. It does not appear to have any particular ethnic distribution, though it is more prevalent in cultures in which intermarriage is an accepted practice.^[2] 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).^[3] NTRK1 is a receptor for nerve growth factor (NGF). This protein induces outgrowth of axons and dendrites and promotes the survival of embryonic sensory and sympathetic neurons. The mutation in NTRK1 does not allow NGF to bind properly, causing defects in the development and function of nociceptive reception.^[4]

In the media

The manga and anime series Loveless features 4 characters, the Zero, with this condition. Notably they were genetically engineered to possess it as their creator believed being unable to feel pain would make them better warriors.

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.

In the original visual novel, as well as the anime adaptation of DRAMAtical Murder, it is stated that of the main characters, Noiz, suffers from this condition.

CIPA is examined in an episode of Mystery Diagnosis entitled The Boy Who Never Cried, featuring a child suffering from the disorder. The child's condition first emerges after the tip of their tongue ulcerates and is accidentally bitten off by the repeated action of it moving against the child's growing incisor teeth.

In the first season of the TV series The Blacklist in the episode "The Courier (No. 85)" (5th episode), the Courier, a criminal transporter, is diagnosed with congenital anhidrosis.

References

External links

• The Facts of Painless People The website of two adults on separate sides of the world who were born with CIPA.
• Help Roberto The website of young boy with CIPA. Features Roberto's specific case, information about CIPA, and links to videos on CNN and the Discovery Channel. (Site has ended, link from Archive.org)