Uric Acid MoleculeThe interaction of mRNA in a eukaryote cell.The exon portion of a DNA strand encodes a specific portion of a protein. In some organisms exons are situated between introns which are spliced from the strand before it is exported from the nucleus and do not code for protein parts.
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Lesch-Nyhan syndrome

Lesch-Nyhan syndrome (LNS) is a rare, inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). LNS is an X-linked recessive disease: the gene is carried by the mother and passed on to her son. LNS is present at birth in baby boys. Patients have severe mental and physical problems throughout life. The lack of HPRT causes a build-up of uric acid in all body fluids, and leads to symptoms such as severe gout, poor muscle control, and moderate mental retardation, which appear in the first year of life. A striking feature of LNS is self-mutilating behaviors, characterized by lip and finger biting, that begin in the second year of life. more...

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Abnormally high uric acid levels can cause sodium urate crystals to form in the joints, kidneys, central nervous system and other tissues of the body, leading to gout-like swelling in the joints and severe kidney problems. Neurological symptoms include facial grimacing, involuntary writhing, and repetitive movements of the arms and legs similar to those seen in Huntington's disease. The direct cause of the neurological abnormalities remains unknown. Because a lack of HPRT causes the body to poorly utilize vitamin B12, some boys may develop a rare disorder called megaloblastic anemia.

The symptoms caused by the buildup of uric acid (arthritis and renal symptoms) respond well to treatment with drugs such as allopurinol that reduce the levels of uric acid in the blood. The mental deficits and self-mutilating behavior do not respond to treatment. There is no cure, but many patients live to adulthood.

LNS is rare, affecting about one in 380,000 live births. It was first described in 1964 by Dr. Michael Lesch and Dr. William Nyhan.


LNS is characterized by three major hallmarks: neurologic dysfunction, cognitive and behavioral disturbances, as well as uric acid overproduction (hyperuricemia). Some may also be afflicted with anemia (macrocytic). Virtually all patients are male, and male victims suffer delayed growth and puberty, and most develop shrunken testicles or testicular atrophy. Female carriers are at an increased risk for gouty arthritis, but are usually otherwise unaffected.

Overproduction of uric acid

One of the first symptoms of the disease is the presence of sand-like crystals of uric acid in the diapers of the affected infant. Overproduction of uric acid may lead to the development of uric acid crystals or stones in the kidneys, ureters, or bladder. Such crystals deposited in joints later in the disease may produce gout-like arthritis, with swelling and tenderness.

The overproduction of uric acid is present at birth, but may not be recognized by routine clinical laboratory testing methods. The serum uric acid concentration is often normal, as the excess purines are promptly eliminated in the urine. The crystals usually appear as an orange grainy material, or they may coalesce to form either multiple tiny stones, or distinct large stones that are difficult to pass. The stones, or calculi, usually cause hematuria (blood in the urine) and increase the risk of urinary tract infection. Some victims suffer kidney damage due to such kidney stones. Stones may be the presenting feature of the disease, but can go undetected for months or even years.

Nervous system impairment

The periods before and surrounding birth are typically normal in individuals with LNS. The most common presenting features are abnormally decreased muscle tone (hypotonia) and developmental delay, which are evident by three to six months of age. Affected individuals are late in sitting up, while most never crawl or walk. Lack of speech is also a very common trait associated with LNS.

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Lesch-Nyhan Syndrome
From Gale Encyclopedia of Medicine, 4/6/01 by G. Victor Leipzig


Lesch-Nyhan syndrome is a severe hereditary disorder that leads to physical and mental retardation, and is often associated with self-destructive biting of the hands and lips.


Lesch-Nyhan syndrome affects 1 in 400,000 live births. Only male children are affected, but women can be asymptomatic carriers and pass the mutation on to their offspring.

Children with Lesch-Nyhan frequently injure themselves due to muscle spasms. They also show aggressiveness toward themselves and others. The most dramatic symptom of Lesch-Nyhan syndrome is the compulsive biting of the lips, tongue, and finger tips which can lead to serious injury and scarring. Over time, serious injury to the kidneys may develop as a result of the excessive uric acid in the blood.

Causes & symptoms

Lesch-Nyhan is caused by a mutation in the gene for the enzyme named hypoxanthine-guanine phosphoribosyltransferase (HPRT). HPRT catalyzes a reaction which is necessary to prevent the buildup of uric acid. Mutation in the HPRT gene leads to an absence of enzyme activity which, in turn, leads to markedly elevated uric acid levels in the blood (hyperuricemia) with further consequences that include urinary tract stones and severe developmental impact on the brain. The disease known as gout is caused by a less damaging mutation in the same gene, leading to reduced--but not eliminated--HPRT activity.

The HPRT gene is located on the X chromosome. Males have only one X chromosome, so any male who inherits the defective X will develop the disease. Women, however, have two X chromosomes. Because the mutant gene is recessive, a woman would need to inherit two defective copies in order to develop the disease. This is impossible because male Lesch-Nyhan patients are not capable of fathering children. As a result, all victims of Lesch-Nyhan syndrome are male. There is a 50% probability that any male child of a carrier will inherit the defective gene.

At birth, patients appear completely normal and often develop normally for the first few months. Often the earliest sign is the presence of sand-like crystals of uric acid in the diapers. The baby may be unusually irritable. The first symptom of nervous system impairment is inability to lift the head at an appropriate age of four to six months. By the end of the first year, writhing motions (athetosis), and spasmodic movements of the limbs and facial muscles (chorea) are clear evidence of defective motor development. Spasticity and palsy are terms used to describe the poor motor coordination of the victims.


Diagnosis is based initially on the distinctive pattern of symptoms and is confirmed by DNA testing.

Prenatal diagnosis is possible by DNA testing of fetal tissue drawn by amniocentesis or chorionic villus sampling. Because Lesch- Nyhan is quite rare, not every fetus should be tested. Fetuses should be tested if the mother is a carrier of the defective HPRT gene. Women who carry a defective HPRT gene and are therefore at risk of bearing an affected fetus can readily be detected by a simple blood test. Any woman related to a HPRT patient should be tested to determine if she is a carrier.


There are no known treatments for the neurological defects of Lesch-Nyhan. The gout medication allopurinol can lower blood uric acid levels and prevent damage to the kidneys. It is important that patients receive adequate fluid intake and that they be restrained when self-destructive behavior occurs.


With strong supportive care, infants born with Lesch-Nyhan can live into adulthood with symptoms continuing throughout life.


At present, there are no preventive measures for Lesch-Nyhan syndrome. However, recent studies have indicated that this genetic disorder may be a good candidate for treatment with gene replacement therapy. Unfortunately, the technology neccessary to implement this therapy has not yet been perfected.

Key Terms

A procedure for sampling fetal cells from the amniotic fluid surrounding the fetus in the womb.
Chorionic villus sampling
A procedure for sampling fetal cells which is performed through the mother's vagina and cervix or through the abdomen.
Uncontrolable tremors.
A spastic condition or state characterized by the sudden, involuntary contraction of one or more groups of muscles.

Further Reading

For Your Information


  • Lesch, M., and W. L. Nyhan. "A Familial Disorder of Uric Acid Metabolism and Central Nervous System Function." American Journal of Medicine 36(1964): 561-570.


  • Alliance of Genetic Support Groups. (This service provides referals to specific disease support organizations.) 4301 Connecticut Ave. NW, Suite 404, Washington, DC 20008. (202) 966-5557. (800) 336-4363.
  • National Organization for Rare Disorders. P.O. Box 8923, New Fairfield, CT 06812-1783. (800) 999-6673.


  • The National Institutes of Health maintain the following web page with information about Lesch-Nyhan syndrome: www.ninds.nih.gov/healinfo/disorder/lesch-nyhan/lesch- nyhan.htm

Gale Encyclopedia of Medicine. Gale Research, 1999.

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