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Credit: pediatricneurosciences.com
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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.
People with this disorder are very likely to injure
themselves in ways that would normally be prevented by feeling pain. For
example, a patient could burn themselves severely and not even notice. 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.
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. 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). 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.
In the media
The manga and anime series Loveless features
a group of four 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.
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.
In the Japanese visual
novel, Dramatical Murder, the character Noiz suffers
from CIPA, and participates in the fighting simulation called Rhyme in order to
feel the illusion of pain.
Ronald Niedermann is an antagonistic character in Stieg
Larsson novel The Girl Who Kicked the Hornets'
Nest, a criminal that born with a "rare condition" that makes him
unable to feel pain.
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