Lesch-Nyhan Disease and Its Variants: Phenotypic and Mutation Spectrum of Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency in Argentine Patients

Abstract Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency is a disorder of purine metabolism responsible for Lesch-Nyhan Disease (LND) and its variants, HPRT-related hyperuricemia with neurologic dysfunction (HND) and HPRT-related hyperuricemia (HRH). The objective of this study was to characterize a cohort of Argentine patients with HPRT deficiency diagnosed in a single center. Results: Twenty nine patients were studied, including 12 LND, 15 HND and 2 HRH. The average onset age was 0.64 years for LND with motor delay as the main manifestation, 8.84 years for HND and 2.5 years for HRH; nephrological manifestations predominated as presenting features in these variants. The average diagnosis age was 3.58 years for LND, 17.21 years for HND and 2.5 years for HRH. Clinical heterogeneity was more evident in HND, even in members of the same family. All patients presented hyperuricemia and no detectable HPRT activity in erythrocyte lysate. The molecular study allowed to identify 9 different mutations in HPRT1 gene from 24 patients (11 independent pedigrees) and to establish genotype-phenotype correlation. In conclusion, this study describes the genotypic/phenotypic spectrum of HPRT deficiency in Argentine patients and highlights the need to increase awareness about the suspicion of these diseases, especially the LND variants with high clinical heterogeneity.

Analysis of diagnosis and treatment of Lesch-Nyhan syndrome / 中华泌尿外科杂志

Objective:To explore the etiology, clinical diagnosis and treatment strategy of Lesch Nyhan syndrome.Methods:We retrospectively analyzed 2 patients with severe dyskinesia, mental retardation and complicated renal calculi who were admitted to the first people's Hospital of Zhengzhou in August 2019. Case 1, male, 9 years old, had multiple urinary calculi for 1 year. The patient came to the local hospital because double multiple kidney stones and bladder stonesa year ago. The patient had been treated with transurethral holmium laser lithotripsy for bladder stones. The results of infrared spectrum showed that the bladder stone was anhydrous uric acid stone. A week ago, color Doppler ultrasound showed multiple kidney stones and bladder stones. The patient was underdeveloped, mentally retarded and had a full-term cesarean section. There was no history of hypoxia, asphyxia and rescue of the patient. He had the following clinical manifestations: In the waking state, he was no language response to any stimulation. The nasolabial fold on the right was shallow and the corner of the mouth was oblique to the left. He lost the large movements such as lifting head, sitting alone, standing. The trunk showed torsion spasticity, limb muscle strength 2-3, limbs showing spastic hypertonia, limb joints stiff, hands showing fist-like, no involuntary movement and muscle fasciculation. The biceps reflex and knee tendon reflex were not elicited, and the pathological reflex was positive. Serum uric acid was 517 μmol/L. The Case 2 came from the same family, male, 6 years old, had the similar symptoms to his elder brother case 1. The family members complained on behalf of the child about intermittent fever for more than 2 years. The imaging examination of case 2 revealed kidney stones. Serum uric acid was 373 μmol/L. Whole Exome Sequencing and Sanger Sequencing were used to find the genetic causes of the two siblings. The NCBI-Homologene database was used to find the homologous sequence of the human HPRT1 gene, and the human HPRT1 gene sequence was compared with other species to analyze the protein conservation. The online website PredictProtein (http: //www.predactprotein) was used to predict the two-dimensional structure of the HPRT1 gene. The reported cases were summarized and same with the treatment plan.Results:A De novo mutation [c.571T>G(p.Tyr191Asp)] was found in the HPRT1 gene of the child, which was inherited from the mother. Lesch Nyhan syndrome can be diagnosed by the results of gene examination combined with clinical manifestations. The amino acid Tyr at the 191 position and the amino acids before and after it were highly conserved. Amino acid 191 was involved in the β-strand of the protein. We treated the patients with the lowest dose of allopurinol and children's conventional dose of potassium sodium bicitrate granules, and low purine diet. After 3 months of treatment, the serum uric acid was decreased, and the urinary calculi did not increase significantly.Conclusions:Combining with the clinical manifestations of children, HPRT1 gene might be the cause of pediatric disease and the two siblings could be diagnosed as Lesch-Nyhan syndrome. For such patients, the lowest dose of allopurinol and children's conventional dose of potassium sodium hydrogen citrate granule combined with diet could be more effective.

A Case of Lesch-Nyhan Syndrome Manifesting Only Chronic Gouty Arthritis without Neurologic Symptom

Deficiency of hypoxanthine-guanine phosphoribosyltransferase is a purine nucleotide disorder and is the most common genetic cause of uric acid overproduction. This disease has a wide range of spectrum with regard to neurological features depending on the extent of the enzymatic deficiency. Complete deficiency of hypoxanthine-guanine phosphoribosyltransferase, called Lesch-Nyhan syndrome, is presented with hyperuricemia and characteristic neurological manifestation and self-mutilation. Partial hypoxanthine-guanine phosphoribosyltransferase--deficient patients are presented with a various intensities of the aforementioned symptoms, from almost normal neurologic manifestation to a severe form along with hyperuricemia. We report a twenty-year-old man with complete hypoxanthine-guanine phosphoribosyltransferase mutation and Lesch-Nyhan sydrome, who manifested gouty arthritis without neurologic symptom.

A Case of Lesch-Nyhan Disease Manifesting Gouty Arthritis without Self-mutilation / 대한신장학회지

Lesch-Nyhan disease is a very rare X-linked recessive disorder characterized by mental retardation, spasticity resembling cerebral palsy, choreoathetosis, self-mutilation and hyperuricemia. Self-mutilative behavior is a hallmark of the disease. The underlying defect is a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT). We report on a fourteen-year-old boy, who manifested gouty arthritis and mild renal insufficiency with Lesch-Nyhan disease, lacking self-mutilative behavior in spite of undetectable HPRT activity. Though there were several reports about some cases of Lesch-Nyhan disease in the past Korean literature, the cases were classic forms with definite neurological manifestation. As far as we know, this is the first case of Lesch-Nyhan disease without self-mutilation in Korea.

A Case of Partial Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency Presenting as Uric Acid Lithiasis / 소아과

The deficiency of enzyme hypoxanthine-guanine phosphoribosyltransferase(HPRT) results in hyperuricemia and subsequently manifests in diverse symptoms. Lesch-Nyhan syndrome is a disorder characterized by hyperuricemia, mental retardation, choreoathetosis, spasticity and self-mutilation, resulting from complete deficiency of the enzyme, whereas partial deficiency of the enzyme shows symptoms of milder forms more often without abnormal neurologic signs. A 7-year-old boy with normal growth and psychomotor development presented with a uric acid stone accompanied by a disproportionate increase of serum/urine uric acid level. The stone was removed by nephrolithotomy and further enzymatic study on lysed erythrocytes showed less than 1% of the normal HPRT activity. After initiation of treatment with allopurinol, the uric acid level was rapidly decreased to a normal range and the patient has not shown hyperuricemia or nephropathy since. Although partial HPRT deficiency is not commonly seen, this possibility should be considered whenever urolithiasis is accompanied by disproportionately high levels of serum uric acid.

Molecular analysis of hprt mutation in B6C3F1 mice exposed to ozone alone and combined treatment of 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone and/or dibutyl phthalate for 32 and 52 weeks

Potential toxicological interactions of 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and/or dibuthyl phthalate (DBP) on ozone were investigated after 32- and 52-wk exposures using hprt mutation assay. Male and female B6C3F1 mice exposed to ozone (0.5 ppm), NNK (1.0 mg/kg), DBP (5,000 ppm), and two or three combinations of these toxicants 6 h per day for 32- and 52-wk showed increases in the frequencies of TG rlymphocytes compared to the control groups. Additive interactions were noted from two combination groups compared to the ozone alone in both sexes of 32- and 52-wk studies. The most common specific mutation type in the hprt genes of test materials-treated male and female mice was transversion with very few transition. The results indicate that such dominant transversion may be responsible for toxicity and combined exposure to ozone, NNK, and DBP induces additive genotoxicities compared to ozone alone.

Partial HPRT Deficiency Due to a Missense Mutation in the HPRT Gene

An 8-month-old male infant presented with persistent, gross, orange-colored crystals in his urine. His physical and neurological development was normal. Laboratory study showed hyperuricemia, hyperuricosuria and urate crystaluria. He was determined to have partial hypoxanthine-guanine phosphoribosyl transferase(HPRT) deficiency. The molecular genetic analysis revealed a missense mutation in the patient's HPRT gene. By sequencing the patient's cDNA, we identified an A-to-G transition at nucleotide 239, resulting in the replacement of Aspartate with Glycine at amino acid 80 in the HPRT. To our knowledge, this mutation has not previously been reported. Our patient is now being placed on allopurinol therapy, and has had no problem since. Partial HPRT deficiency has been known to cause recurrent acute renal failure without the phenotypic features of Lesch-Nyhan syndrome. Therefore, we think that early diagnosis and treatment are very crucial in preventing acute renal failure.

A Case of Lesch-Nyhan Syndrome

Lesch-Nyhan syndrome is an X-linked recessive disorder characterized by hyperuricemia, choreoathetosis, spasticity, mental retardation, and compulsive, self-injurious behavior. This disorder results from a complete deficiency of the purine salvage enzyme, hypoxanthine-guanine phosphoribosyl transferase(HPRT). We report here on a case of Lesch-Nyhan syndrome in a 1-year, 7-month-old male who presented with frequent vomiting, failure to thrive, and developmental delay. The diagnostic work-up revealed hyperuricemia, hyperuricosuria, and medullary nephrolithiasis. The HPRT activity in the erythrocytes was undetectable with a biochemical assay. We also identified de novo mutation which was a deletion of the 649th base, adenosine, in HPRT gene(649delA) by analysis of cDNA using RT-PCR technique coupled with direct sequencing.

Molecular characterization and Prenatal Molecular Evaluation of three fetuses in four unrelated Korean families with Lesch-Nyhan syndrome

The Lesch-Nyhan syndrome which is caused by the deficiency of hypoxanthine guanine phosphoribosyltransferase is an X-linked recessive disorder characterized by hyperuricemia, choreoathetosis, mental retardation and compulsive self-injurious behavior. Clinical management of the patients with the Lesch-Nyhan syndrome is frustrating and requires burdensome medical treatment since it cripples the patient and shortens the life span by progression of neurological symptoms, but there are no cures or measures for relieving relentless natural course of the disease yet. Therefore, prenatal diagnosis of the affected fetus is important in genetic counselling for the family at high risk. In this study, four different mutations in the HPRT gene of four probands have been identified in four unrelated families; K215X, Q109X, nt.631 A, and nt.289 GT. Two mutations among them altered restriction enzyme sites; SpeI for Q109X and MaeI for nt.289 GT. Based on their molecular defects, prenatal diagnoses of 3 the fetuses were successfully made between ninth and eleventh week of gestation by polymerase chain reaction(PCR), restriction digestion and DNA sequencing using cDNA obtained from chorionic villus samples (CVS). We predicted the outcome of all fetuses prenatally. Among the three fetuses two were male and one was female according to the identification made by PCR amplification of the sex determining region of the Y chromosome(SRY) gene. Each carried a wild type allele for the corresponding mutant allele. They were also tested postnatally for the mutations to be unaffected.

Inactivation of mammalian X-chromosome during spermatogenesis: Temporal expression of genes in the laboratory mouse.

At zygotene/pachytene stage of meiosis in mammalian testis, the X—Y heterobivalent is sequesterd into a heterochromatinized body whose genetic inactivity is shown by lack of uridine incorporation. For the genic level evaluation of the X-inactivation, activities of three X-linked genes were assayed in testicular cell types in the laboratory mouse. While hypoxanthine phosphoribosyl transferase is functional at least up to pachytene stage of primary spermatocytes, glucose-6-phosphate dehydrogenase appears to be active only in the Sertoli cells. No transcript of the muscle specific muscular dystrophin gene was obtained from its regular 5' promoter. Thus, inactivation of X-linked genes in testis occurs at different stages during spermatogenesis, independently of heterochrornatinizati on of the XY-body. We propose that Xist transcript, the putative regulator of X-inactivation in female soma, is also the regulator in testis. However, due to its extremely low level in testis the transcript may regulate by "spreading" in a gradient and affect the genes in a temporal order. Thus, besides other factors, physical proximity of the genes to Xist may determine the stage of their inactivation.

Construction and application of a mouse HPRT targeting vector with Cre recombinase recognition site lox66 / 第二军医大学学报

Objective: To study the construction and application of a vector with Cre recombinase recognition site lox66 for mouse HPRT gene targeting in embryonic stem(ES) cells. Methods: Using the HPRT genomic DNA fragment and synthesized oligonucleotides, pSP HPRT lox66 Neo was designed and constructed as a replacement vector by common molecular cloning techniques. After the linearized pSP HPRT lox66 Neo DNA was electroporated into ES cells, and transfected cells were cultured in G418/6 TG drug selection medium. The recombination efficiency of this vector was tested. Results: The main components of pSP HPRT lox66 Neo were a positive selection gene Neo, lox66, long and short homologous fragments of mouse HPRT gene and plasmid backbone. Twenty ES cell clones with HPRT gene inactivated were obtained. Conclusion: An effective replacement vector with Cre recombinase recognition site lox66 is constructed and applied to HPRT gene targeting in ES cells.