There are a lot of awful diseases out there, but this genetic disorder is particularly gruesome. It causes people to cannibalize themselves, and no one is entirely sure why.
Lesch-Nyhan syndrome is caused by a single faulty gene on the X chromosome. As with hemophilia, females, who have two X chromosomes, are usually asymptomatic carriers of the gene - only a single female case has been reported. Males feel the effects, and it's one of the more horrible diseases out there.
The faulty gene codes for an enzyme called hypoxanthine guanine phosphoribosyl transferase (HGPRT), which is vital to the recycling system in living cells. Cells are often breaking down the DNA inside them to its component parts. These parts, in turn, need to be broken down. Two of these parts, adenine and guanine, need to be broken down by HGPRT. In the absence of an enzyme that can break them down properly, the compounds build up until they decompose into uric acid. Uric acid irritates the cell before moving into the blood and causing crystals in the urine - otherwise known as kidney stones. This is one majore symptom that helps doctors to diagnose a person with Lesch-Nyhan syndrome.
A more horrible symptom is a specific kind of self-injury. People with Lesch-Nyhan syndrome bite their lips, tongue, and chew their fingers. Sometimes the injuries are just unpleasant and scarring - but people have been known to chew off their tongues and fingers. The behavior is so common that it's considered characteristic of the syndrome, and has given it the nickname of "self-cannibalization syndrome."
Doctors still don't know why this behavior occurs. The simplest explanation is that the uric acid irritates the cells, and people bite at their most sensitive tissues the way other people will scratch a mosquito bite until it bleeds. Another theory is that the effects of uric acid on a developing brain causes a lack of dopamine. A chilling theory posits that Lesch-Nyhan syndrome is the opposite of Parkinson's disease. People with Parkinson's can't seem to initiate the actions they are thinking about doing, but people with Lesch-Nyhan syndrome can't stop themselves from doing the things they think about. If they think about biting themselves, they will do it, even if they don't want to. Yet another theory has it that injury causes a release of dopamine in the brain. One accidental injury to the face or hands causes a rush of good feelings that makes people with the syndrome injure themselves more.
There probably is a psychological component to the injury. One treatment for the compulsive biting is complete removal of teeth. Individuals who undergo this stop biting themselves, but often scratch and gouge at their faces. Something causes them to keep hurting themselves.
Lesch-Nyhan syndrome is genetic, and women with a history of it in their family can get screened for it to see if they are a carrier prior to pregnancy. So far, there is no cure for the disease, only management of the symptoms.
Image: Ed Uthman
[Via Case Report: The Lesch-Nyhan Syndrome, Lesch-Nyhan Syndrome, Lesch-Nyhan Syndrome Self-Injurious Behavior.]