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At a glance

It is a rare inborn error of purine metabolism that becomes apparent between the ages of 3 and 6 months. It is characterized by the presence of orange crystal-like deposits (“orange sand”) in the diapers of infants with the disorder. This is frequently the first symptom of Lesch-Nyhan Syndrome. Other clinical features include hematuria, urinary tract infections, arthritis, choreoathetosis manifested by raising and lowering of the shoulders, and facial grimacing. Hypotonia, hypertonia, hyperreflexia, and spasticity have been reported. Megaloblastic anemia, self-mutilating behavior, irritability screaming, uncontrolled aggressiveness, and compulsive actions complete the clinical presentation.

Synonyms

Juvenile Gout; Nyhan Syndrome; Hyperuricemia Syndrome; Hypoxanthine-Phosphoribosyl-Transferase Deficiency Disease; Complete HGPRT Deficiency Disease; Kelley-Seegmiller Syndrome; Hyperuricemia-Oligophrenia Syndrome.

History

The disorder was first recognized and clinically characterized by a medical student Michael Lesch (1939-2008) and his mentor, William Nyhan (b. 1926), currently Professor of Pediatrics at the University of California San Diego School of Medicine in La Jolla, who published their findings in 1964.

Nature

Genetically transmitted error of metabolism of purine bases.

Incidence

Estimated at 1:380,000 live births in the United States. It affects males and in very rare cases, females have been reported with the disorder. However, in most cases, females may be carriers of the disease gene, but do not exhibit any symptoms. They are considered heterozygotes mild form of the disease.

Genetic inheritance

It is estimated inherited as X-linked (Xq26-Xq27) recessive disorder and caused by a mutation in the gene coding for the enzyme hypoxanthine phosphoribosyltransferase (HPRT). Different mutations have been described.

Pathophysiology

The mutation leads to total or partial loss of function of HPRT, which normally catalyzes the conversion of hypoxanthine and guanine to inosinic and guanylic acid, a reaction that allows reuse of preformed purine bases resulting from cell turnover and catabolism. The absence of this reaction results in overproduction of uric acid and leads to hyperuricemia and uricosuria and thus urate nephropathy, urinary tract calculi, and gout. The neurologic features of the syndrome (choreoathetosis, self-mutilation, spasticity) are caused by abnormalities in brain neurotransmitters, mainly decreased dopaminergic activity in the basal ganglia. Treatment with inhibitors of xanthine oxydase (allopurinol 10 mg/kg/day, maximum 800 mg/day) can control hyperuricemia but does not prevent the effect on neurologic system. This medical condition is associated with a poor prognosis with few patients that live beyond age 40 years.

Diagnosis

Patients are normal at birth and the onset of symptoms appears within few months in infancy. Diagnosis can be clinically evocated by the observation of orange crystals in the diapers or crystalluria with obstruction of the urinary tract. Psychomotor retardation appears quickly (delay in acquisition of sitting and head support), followed by spasticity and athetoid movements. Self-mutilation ...

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