Congenital Insensitivity to Pain
A person with congenital insensitivity to pain never feels any physical pain from the start of his or her life. This is a very dangerous disease as these people may not be able to determine if a bone is broken or if they have bitten off the tip of their tongue unless they see the swelling of the surrounding tissue or taste blood in their mouth. Because of this inability to sense pain, it is common for patients with congenital insensitivity to pain to have unseen infections as well as have a multitude of bruises, wounds, and broken bones over their lifetime. It is important to note, however, that persons with congenital insensitivity to pain do not have cognitive defects and they have normal light and crude touch sensations. This means they can sense sharp and dull pressures on their skin. Temperature sensation may be normal. People with congenital insensitivity to pain can tell if something is hot or cold to the touch, but they are not able to sense pain caused by extremely hot temperatures, which is abnormal. For example, they may not realize that by touching a hot stove, they are burning their skin.
In general, persons with congenital insensitivity to pain have a shortened life expectancy, as they have repeated burn injuries. Most of these burns are severe (third-degree burns) and may become a life-threatening injury. Additionally, children with congenital insensitivity to pain tend to have mouth wounds because they do not know that they are biting their tongue or cheek, and tend to have finger and hand injuries.
Other disorders that have difficulty with pain and touch sensitivity are autism and its related autistic-spectrum disorders like Asperger’s syndrome. These disorders are associated with an overall dysfunction of the sensory system, and pain or touch insensitivity can be one of the symptoms of the syndrome.
Anatomy and Physiology
Congenital insensitivity to pain is considered to be a neuropathy of the peripheral nervous system as it is a sensory system dysfunction. Recent studies have identified a mutation in the SCN9A (sodium channel, voltage gated, type IX alpha subunit) gene that causes congenital insensitivity to pain. The SCN9A gene codes for part of a sodium channel, specifically the NaV1.7 channel. These sodium channels are found in pain fibers (nociceptors) and are essential in transmitting pain from the periphery to the central nervous system. Defects in the SCN9A gene cause the NaV1.7 channel to not be formed or made, thus sodium is not able to enter the channel and transmit the pain signal. NaV1.7 channels are also found in olfactory sensory neurons. This means that many persons with congenital insensitivity to pain will also have anosmia, or the inability to smell.
Congenital insensitivity to pain is a very rare disease with less than 50 cases found in scientific literature. It is an autosomal recessive gene dysfunction, which means that both copies of the SCN9A gene must have a defect. Thus, a person with congenital insensitivity to pain must receive a mutated SCN9A gene from both his or her mother and father. The parents of children with congenital insensitivity to pain are considered to be carriers as they have at least one mutated gene. The parents generally do not have any signs or symptoms of abnormal perception of pain nor do they have congenital insensitivity to pain.
Jennifer L. Hellier
See also: Anosmia; National Organization for Rare Disorders; Nociception; Sensory Receptors; Somatosensory Cortex; Somatosensory System
Capsoni, Simona, Sonia Covaceuszach, Sara Marinelli, Marcello Ceci, Antonietta Bernardo, Luisa Minghetti, … Antonino Cattaneo. (2011). Taking pain out of NGF: A “painless” NGF mutant, linked to hereditary sensory autonomic neuropathy Type V, with full neurotrophic activity. PLoS One, 6(2), e17321.
Genetics Home Reference: Your Guide to Understanding Genetic Conditions. (2010). Congenital insensitivity to pain. U.S. National Library of Medicine. Retrieved from http://ghr.nlm.nih.gov/condition/congenital-insensitivity-to-pain
Golshani, Ashkahn E., Ankur A. Kamdar, Susanna C. Spence, & Nicholas M. Beckmann. (2014). Congenital indifference to pain: An illustrated case report and literature review. Journal of Radiology Case Reports, 8(8), 16—23. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4242143/