Congenital insensitivity to pain — or CIP, for short — is a term used to describe the inability to feel physical pain, and a few rare genetic disorders cause it.
People who have CIP can't feel any physical pain from birth, and they often have other sensory problems, such as being unable to smell or unable to feel extremely cold or hot temperatures. CIP is typically autosomal recessive, which means that a child needs to have two copies of a mutated (changed) gene passed down from their parents to have CIP.
What Causes CIP?
Also called congenital analgesia or congenital indifference to pain, congenital pain insensitivity is a kind of peripheral neuropathy — specifically, a type of hereditary sensory and autonomic neuropathy, or HSAN.
Nociception is the nervous system's ability to feel painful sensations. It uses nociceptors, which are specialized nerve cells that detect tissue damage.
People with congenital insensitivity to pain have nociceptors that don't work correctly — they're either undeveloped or don't respond to pain signals the way most people's nociceptors do. Without nociceptors that work, the nervous system can't send messages about painful sensations to the brain, so people with CIP can't feel physical pain.
CIP is rare — some of its phenotypes (sets of genetic traits - in this case, traits of genetic disorder) are documented in only one family. Only a few hundred cases of most of its more common phenotypes are reported worldwide.
What Gene Causes Congenital Insensitivity to Pain?
The most common causes of CIP are mutations in the SCN9A or NTRK1 genes. They lead to various HSAN phenotypes of CIP:
Congenital insensitivity to pain with anhidrosis. Abbreviated as CIPA, it's regarded as the HSAN4 phenotype. It's characterized by the inability to feel physical pain and the inability to sweat from birth. People with CIPA often have recurrent fevers, an inability to perceive temperature extremes, developmental delays, behavioral problems, and hypotonia.
Hyperthermia, where your body temperature goes uncontrollably high, is dangerous for people with CIPA since their bodies can't regulate temperature through sweating. People with CIPA also typically have frequent infections, especially from Staphylococcus aureus, which are often resistant to antibiotics.
Familial dysautonomia. This phenotype is considered to be HSAN3. It mainly affects people of Eastern European Jewish descent and is characterized by low sensitivity to pain, hypotonia, lack of tear production, poor growth, and difficulty in maintaining a stable body temperature and blood pressure.
Crying without tears as an infant is often the first sign of familial dysautonomia, which is noticed by parents or doctors. Scoliosis is found in 95% of people with familial dysautonomia by their teenage years. Weakness, leg cramping, and insomnia may develop. Kidney disease is common in adults with familial dysautonomia.
Channelopathy-associated congenital anesthesia. Regarded as the HSAN2D phenotype, it's also called channelopathy-associated congenital insensitivity to pain. It's caused by mutations in the SCN9A gene or, rarely, in the PMRD12 gene. People with channelopathy-associated congenital anesthesia can't feel physical pain partly because their body makes too many endogenous opioids — the body's natural painkillers produced in the brain. People with channelopathy-associated congenital anesthesia often have anosmia, which is the partial or total loss of the sense of smell.
Is Congenital Insensitivity to Pain Good?
While it may sound pleasant to go through life without physical pain, congenital insensitivity to pain is a harmful condition, which often shortens the lifespan of people who have it.
Pain acts as a warning system for your body, alerting you to illnesses and injuries. The instinct to avoid pain also keeps you from taking part in dangerous activities. If you can't feel any pain, you may not notice a severe injury or you may seriously hurt yourself by accident — for example, you may place your hand on a stove burner. Without pain, you don't have the natural instinct to protect wounds from being bumped or scraped, and this can lead to the worsening of your injuries and infections.
Medical emergencies that would usually cause you to seek medical help because of pain — like appendicitis or a heart attack — can go completely unnoticed by someone with CIP. They may also not notice if they have fractures, dislocations (where bones are forced out of their normal position), and joint damage. This can gradually cause long-term deformity and disability.
People with CIP need to routinely examine themselves to check for injuries they haven't noticed. The high likelihood of accidental injury and poor wound healing can reduce their life expectancy.
What are the Symptoms of CIP?
Most people with congenital insensitivity to pain will show the following symptoms:
- Pain insensitivity — where there's no reaction to painful sensations caused by cuts, burns, or injections
- Repeated severe injuries and accidental self-injury — like severe bite wounds on the tongue, mouth, and fingers
- Anhidrosis — or hypohidrosis, the reduced ability to sweat
- Anosmia
- No reaction to extreme temperature
- Recurrent high fever — possibly with febrile seizures
- Lack of corneal reflex — which is when you blink as a reflex to something touching your cornea
- Intellectual disability
CIP symptoms can vary among people with the condition — you may see either a few or several of these symptoms in one person with CIP. While congenital insensitivity to pain is extremely rare, check with your child's doctor if they don't respond to pain or repeatedly injure themselves.
How is Congenital Insensitivity to Pain Diagnosed?
CIP is often diagnosed in early childhood due to a lack of typical pain response (wincing or crying) during standard medical procedures like vaccination and treatment for common childhood injuries like falls. Accidental self-injury is common among young children with CIP — this includes aggressively biting the mouth, tongue, and fingers to the point of causing severe damage.
Your doctor will diagnose congenital insensitivity to pain by testing your baby's pain response to pricking with something that typically causes pain but doesn't cause damage or scarring, like a needle. To confirm the results of this test, your doctor may recommend genetic testing.
Because CIP is very rare but can cause severe accidental injuries, a child with congenital insensitivity to pain may initially be mistakenly regarded as a victim of child abuse.
How is Congenital Insensitivity to Pain Treated?
There is currently no cure for CIP, so its treatment mainly focuses on patient education — which includes teaching the patients how to avoid injuries, check themselves for any injuries, and get treatment for these injuries as quickly as possible.
In some cases, doctors may suggest preventative medical procedures, like the removal of primary teeth, to prevent young patients from injuring themselves before they can learn how to protect themselves.
An opioid antagonist called Naloxone has been explored as a treatment option for channelopathy-associated congenital insensitivity to pain and has shown partial success in some cases.