(Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency or HPRT Deficiency, Lesch-Nyhan Disease)
Lesch-Nyhan syndrome is a genetic disorder. It affects the metabolism of purines in the body. Purines are protein molecules that are important for the metabolism of RNA and DNA, which make up our genetic codes. Lesch-Nyhan syndrome is characterized by uric acid build-up and self-injury. It occurs mainly in males. This disease is rare; it occurs in 1 of every 100,000 males.
Lesch-Nyhan syndrome is caused by a mutation or change in a gene. This change results in the absence of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). HPRT is needed to metabolize uric acid. Without this enzyme, uric acid builds up in the central nervous system, kidneys, and other areas of the body.
This gene mutation occurs on the X chromosome. It can either be a new mutation in the affected person or inherited from his mother, who is a carrier.
A risk factor is something that increases your chances of getting a disease or condition. Risk factors for developing Lesch-Nyhan syndrome include:
- Sex: Male
- Having male family members on the mother's side of the family with Lesch-Nyhan syndrome
The first symptom of Lesch-Nyhan syndrome is orange-colored crystal-like deposits in the diaper. This may occur in children as young as three months. These deposits are caused by increased uric acid in the urine. Other symptoms include:
- Nervous system impairment:
- Age 4-6 months: lack of muscle tone and inability to lift the head
- Age 6 months: unusual arching of the back
- Age 9 months: inability to crawl or stand
- Age 12 months: inability to walk
- Age 12+ months: spasms of the limbs and facial muscles
- Kidney stones
- Blood in the urine
- Pain and swelling of joints
- Difficulty swallowing (dysphagia)
- Impaired kidney function
Self-mutilating behavior is the hallmark of this disease. Children begin to bite their fingers, lips, and the insides of their mouths as early as two years old.
As children grow, self-injury becomes increasingly compulsive and severe. Eventually, mechanical physical restraints will be necessary to prevent head and leg banging, nose gouging, loss of fingers and lips from biting, loss of vision from eye rubbing, etc. In addition to self-injury, older children and teens will become physically and verbally aggressive.
The cause of these behaviors is not entirely understood. However, some experts believe it is related to abnormalities in brain chemicals called neurotransmitters. It should be stressed that the child does not want to hurt himself or others, but is incapable of preventing these behaviors. People with Lesch-Nyhan syndrome have been described as “doing the opposite” of what they really want.
The doctor will ask about symptoms, behavior traits, and medical history, and perform a physical exam. Tests may include:
- Measurement of HPRT enzyme activity–to confirm the diagnosis
- Molecular genetic testing of the HPRT1 gene–to confirm the diagnosis and to detect if an unaffected female is a carrier of the gene mutation
There is no treatment to cure Lesch-Nyhan. However, certain medications may help to alleviate some of its symptoms. For example:
- To control excessive levels of uric acid in the body:
- Allopurinol (Aloprim, Zyloprim)
- To help reduce some of the problem behaviors:
- Diazepam (Diastat, Valium)
- Haloperidol (Haldol)
- Phenobarbital (Barbita, Luminal)
- A single 2006 report suggests that administration of s-adenosylmethionine (a food supplement now widely available in “health” stores that is naturally synthesized by the human body and important for many bodily processes) may reduce self-mutilating behaviors in adults with this syndrome.
With treatment, the average life expectancy is early- to mid-20s, and there may be an increased risk of sudden death due to respiratory causes. However, many patients live longer with good medical and psychological care.
There are no guidelines to prevent Lesch-Nyhan syndrome. If you have a family history of this condition, you can talk to a genetic counselor when deciding whether or not to have children.