Pain. A four-letter word that can mean so much or so little, depending on who you are. But for all of us, it serves an important purpose: that of keeping us alive. When you burn your hand while attempting (unsuccessfully) to make roast dinner for your family, you know that you should run it under water because the burn – put simply – hurts. Indeed, it is pain that stops you from keeping your hand on that hot surface. Of course, you already know this. But people will do anything to relieve their pain, ranging from the benign actions of changing diets or applying lotions, all the way up to taking opioids. Pain is painful. Who would have known! It keeps you alive by making you suffer, and in some patients, especially older people, it is almost ever present and drastically decreases their quality of life. Yet, while most of us fail to appreciate what pain does for us, there have been around 300 people who face a terrible reality: a world without pain. 

Congenital insensitivity to pain (CIP), or congenital analgesia, is a condition in which the patient is born without the ability to feel physical pain. It is caused by a mutation in the SCN9A gene, which provides instructions for making sodium channels that help transport sodium ions into cells, which is a way for the body to create and relay electrical signals. More specifically, the SCN9A gene codes for the Nav1.7 channel, which (in a healthy body) would usually be found at its highest rate in neurons in the dorsal root ganglion in the spine. When the mutation occurs, the loss of function in these neurons causes the ability to feel pain to be severely damaged, as the dorsal root ganglia are highly involved in nociception: the body’s ability to detect painful stimuli.

In a healthy body, pain is relayed around the body through different varieties of fibres. The A-delta fibres transmit what we would call acute pain—the sudden and sharp feeling you get when your finger touches a hot surface. The C fibres, which are unmyelinated –  meaning that they send electrical impulses at a slower rate as they are not insulated – are responsible for the lasting feeling of pain; this would be the feeling of pain which you still feel minutes after the burn. In a patient with CIP, these signals cannot be sent, as the ion channels which assist the transmission of these impulses are affected by the mutation. 

The consequences to those who suffer from CIP can be disastrous. In an interview with the BBC, Steven Pete recounted that he had chewed off a quarter of his tongue while teething before doctors had concluded that he had congenital insensitivity to pain, and that once, he had only realised his right arm had been broken when he saw a bone sticking out. Of course, experiences vary. A type of CIP called congenital insensitivity to pain with anhidrosis not only prevents feeling pain, but also prevents sweating, causing almost 20% of people to die within their first 3 years due to hyperthermia (as opposed to hypothermia), which is when the body’s temperature rises too high and eventually causes organ failure and thus, death. 

The absence of pain does not allow for “superhuman” physical capabilities as some might presume. A man with CIP described his experience with severe arthritis: although he did not feel pain, there was a “feeling of compression” in his joints which prevented him from moving them around. His brother, before he took his own life, was told by doctors that he would soon have to move around in a wheelchair, partly due to problems with his back. Of course, he did not feel any pain with his back problems, but the ability to feel pain would have prevented those back problems from developing in the first place. 

There is no cure for CIP. Experimental treatments have been tried but rarely have they worked. The most common attempt at treating the disease is by using Naloxone, an opioid antagonist usually used to block the effect of opioids. In this case, it helped to decrease the effects of opioid peptides, which were linked as a potential cause of CIP; a 39-year-old woman, when administered the treatment, was able to feel pain for the first time. The treatment is far from ready however, as with many other rare diseases, it is unlikely that a true cure will be found, as current funding available for this type of research is far too low. 

Congenital insensitivity to pain is a unique condition, in that it makes us realise just how important pain is: pain is what prevents us from being forced to be in a wheelchair before reaching middle age; pain is what prevents us from having to amputate limbs because of continued physical trauma gone unnoticed for far too long; pain screams at us when we have an infection or a wound until it forces us to seek help. 

For many of us, pain is a guardian angel. For some, of course, it can be a devil. But for almost everyone on this planet, without pain, we would be much worse off.


References:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4686868/

https://www.bbc.com/news/magazine-18713585

https://journals.physiology.org/doi/full/10.1152/physrev.00052.2017

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4686868/

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