Juan García Puig

Attenuated variants of Lesch-Nyhan disease

Lesch–Nyhan disease is a neurogenetic disorder caused by deficiency of the enzyme hypoxanthine–guanine phosphoribosyltransferase. The classic form of the disease is described by a characteristic syndrome that includes overproduction of uric acid, severe generalized dystonia, cognitive disability and self-injurious behaviour. In addition to the classic disease, variant forms of the disease occur wherein some clinical features are absent or unusually mild. The current studies provide the results of a prospective and multi-centre international study focusing on neurological manifestations of the largest cohort of Lesch–Nyhan disease variants evaluated to date, with 46 patients from 3 to 65 years of age coming from 34 families. All had evidence for overproduction of uric acid. Motor abnormalities were evident in 42 (91%), ranging from subtle clumsiness to severely disabling generalized dystonia. Cognitive function was affected in 31 (67%) but it was never severe. Though none exhibited self-injurious behaviours, many exhibited behaviours that were maladaptive. Only three patients had no evidence of neurological dysfunction. Our results were compared with a comprehensive review of 78 prior reports describing a total of 127 Lesch–Nyhan disease variants. Together these results define the spectrum of clinical features associated with hypoxanthine–guanine phosphoribosyltransferase deficiency. At one end of the spectrum are patients with classic Lesch–Nyhan disease and the full clinical phenotype. At the other end of the spectrum are patients with overproduction of uric acid but no apparent neurological or behavioural deficits. Inbetween are patients with varying degrees of motor, cognitive, or behavioural abnormalities. Recognition of this spectrum is valuable for understanding the pathogenesis and diagnosis of all forms of hypoxanthine–guanine phosphoribosyltransferase deficiency.

Behavioral aspects of Lesch–Nyhan disease and its variants

Self-injury is a defining feature of lesch-nyhan disease (LND) but does not occur in the less severely affected Lesch-Nyhan variants (LNV). The aim of this study was to quantify behavioral and emotional abnormalities in LND and LNV. Thirty-nine informants rated 22 patients with LND (21 males, 1 female), 11 males with LNV, and 11 healthy controls (HC; 10 males, 1 female) using two well-validated rating scales. The age of patients with LND ranged from 12 years 7 months to 38 years 3 months (mean 22 y 11 mo; sd 7 y 8 mo), whereas the age range of those with LNV was 12 years 9 months to 65 years (mean 30 y 7 mo; sd 15 y 2 mo), and the healthy controls were aged 12 years 4 months to 31 years 3 months (mean 17 y 10 mo; sd 5 y 7 mo). Behavioral ratings were based on the Child Behavior Checklist and the American Association On Mental Retardations Adaptive Behavior Scale--Residential And Community, 2nd edition. Statistical analyses revealed that patients with LND showed severe self-injury together with problematic aggression, anxious-depressed symptoms, distractibility, motor stereotypes, and disturbing interpersonal behaviors. Patients with LNV were rated as being intermediate between the HC and LND groups on all behavior scales. Although the LNV group did not differ from hcs on most scales, their reported attention problems were as severe as those found in LND. We conclude that self-injurious and aggressive behaviors are nearly universal and that other behavioral abnormalities are common in LND. Although patients with LNV typically do not self-injure or display severe aggression, attention problems are common and a few patients demonstrate other behavioral anomalies.

Genotype-phenotype correlations in neurogenetics: Lesch-Nyhan disease as a model disorder

Establishing meaningful relationships between genetic variations and clinical disease is a fundamental goal for all human genetic disorders. However, these genotype-phenotype correlations remain incompletely characterized and sometimes conflicting for many diseases. Lesch-Nyhan disease is an X-linked recessive disorder that is caused by a wide variety of mutations in the HPRT1 gene. The gene encodes hypoxanthine-guanine phosphoribosyl transferase, an enzyme involved in purine metabolism. The fine structure of enzyme has been established by crystallography studies, and its function can be measured with very precise biochemical assays. This rich knowledge of genetic alterations in the gene and their functional effect on its protein product provides a powerful model for exploring factors that influence genotype-phenotype correlations. The present study summarizes 615 known genetic mutations, their influence on the gene product, and their relationship to the clinical phenotype. In general, the results are compatible with the concept that the overall severity of the disease depends on how mutations ultimately influence enzyme activity. However, careful evaluation of exceptions to this concept point to several additional genetic and non-genetic factors that influence genotype-phenotype correlations. These factors are not unique to Lesch-Nyhan disease, and are relevant to most other genetic diseases. The disease therefore serves as a valuable model for understanding the challenges associated with establishing genotype-phenotype correlations for other disorders.

Prevalence of Left ventricular hypertrophy in patients with mild hypertension in primary care: Impact of echocardiography on cardiovascular risk stratification

BACKGROUNDnLeft ventricular hypertrophy (LVH) is an important predictor of cardiovascular risk, and its detection contributes to risk stratification. The aims of the present study were to estimate the prevalence of echocardiographic LVH and to evaluate the influence of echocardiography (ECHO) on cardiovascular risk stratification in hypertensive patients presenting in primary care.nnnMETHODSnIn this cross-sectional study, 250 patients recently diagnosed with mild hypertension underwent clinical evaluation including electrocardiography (ECG), microalbuminuria measurement, 24-h blood pressure monitoring and ECHO. Level of cardiovascular risk was stratified, initially using routine procedures including ECG to assess target organ damage and then again after detection of LVH by ECHO.nnnRESULTSnThe frequency of echocardiographic LVH was 32%, substantially higher than that detected by ECG (9%). Initial cardiovascular risk stratification yielded the following results: 30% low risk, 49% medium risk, 16% high risk, and 5% very high risk subjects. The detection of LVH by ECHO provoked a significant change in the risk strata distribution, particularly in those patients initially classified as being at medium risk. In this group, 40% of subjects were reclassified as high risk subjects according to ECHO information. The new classification was as follows: 23% low risk, 30% medium risk, 42% high risk, and 5% very high risk subjects.nnnCONCLUSIONSnA substantial proportion of mildly hypertensive patients presenting in primary care have LVH determined by ECHO. Our results suggest that this procedure could significantly improve cardiovascular risk stratification in those patients with multiple risk factors, but no evidence of target organ damage by routine investigations.

Update on the Phenotypic Spectrum of Lesch-Nyhan Disease and its Attenuated Variants

Congenital deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) results in a spectrum of clinical phenotypes. All of these phenotypes are associated with marked overproduction of uric acid and related problems such as hyperuricemia, urate nephrolithiasis, tophi, and gout. The mildest phenotypes include only problems related to overproduction of uric acid. The most severe phenotype is known as Lesch-Nyhan disease, in which the phenotype also includes severe motor handicap, intellectual disability, and self-injurious behavior. In between these two extremes is a continuous spectrum of phenotypes with varying degrees of motor and cognitive handicap but no self-injurious behavior. The pathogenesis of overproduction of uric acid in HPRT deficiency is well-understood, and treatments are available to control it. The pathogenesis of the neurobehavioral problems is less well-understood, and effective treatments for them are lacking.

Interaction of Leishmania mexicana promastigotes with the plasminogen–plasmin system

The binding of human plasminogen and plasmin to the promastigote form of Leishmania mexicana was investigated. L. mexicana was capable to bind both molecules, the binding being inhibited by epsilon-aminocaproic acid. Scatchard plot analysis revealed a dissociation constant (Kd) value of 2.4+/-0.8 microM and 0.9+/-0.1 x 10(4) binding sites per cell for plasminogen and a Kd value of 1.2+/-0.4 microM and 1.6+/-0.2 x 10(5) binding sites per cell for plasmin. C-terminal lysine residues are involved in plasminogen binding to cells, since carboxypeptidase B treatment reduced this binding by 34%. Ligand blotting analysis showed a group of proteins, with molecular masses between 105 and 115 kDa, capable to interact with plasminogen. Zymogram analysis showed that the protease activity acquired by L. mexicana, due to the interaction with either plasminogen or plasmin, comprises an important fraction of the total protease activity at pH 7.7. Plasminogen activation by tissue-type plasminogen activator (t-PA) was enhanced by the presence of L. mexicana promastigotes. These results raise the question whether the interaction of L. mexicana with components of the fibrinolytic system is involved in the virulence of the parasite.

Renal handling of uric acid in gout: Impaired tubular transport of urate not dependent on serum urate levels

Metabolic studies were conducted in 56 patients with primary gout and in ten normal subjects to assess differences in the tubular transport mechanisms of urate. Renal handling of uric acid was examined by means of pyrazinamide and probenecid tests at increased and pharmacologically reduced serum urate concentrations in both groups. Patients with gout showed similar serum urate levels and glomerular filtration rates than controls at both serum urate levles. Pyrazinamide decreased urinary uric acid excretion to less than 1.0% of the urate filtered load in both groups at increased and diminished serum urate concentrations. The maximum uricosuric response promoted by probenecid at high serum urate levels was (mean ± SD) 3,707 ± 443 μg/min/1.73 m2 in controls and 2,215 ± 738 μg/min/1.73 m2 in patients with gout (P < 0.01). Forty-four patients had a daily uric acid excretion rate below 700 mg/1.73 m2, and all of them showed a diminished uricosuric response to probenecid. When serum urate was reduced in normal subjects and 30 patients to a mean of 2.1 and 2.3 mg/dL, respectively, probenecid elicited a significantly lower urate excretion rate in gout (532 ± 202 μg/min/1.73 m2) than in controls (922 ± 136 μg/min/1.73 m2; P < 0.01). Among these 30 patients examined in their basal state and at decreased serum urate levels, uric acid excretion following probenecid was normal in six and diminished in 24 in both situations. The difference between maximum uricosuria and basal urate excretion was not increased in gouty patients. [2-14C]uric acid kinetics showed a metabolic clearance rate of 6.3 ± 1.5 L/24 h/m2 in five gouty normoexcretors and 3.5 ± 0.8 L/24 h/m2 in three underexcretors (P < 0.01), classified according to both 24-hour uric acid excretion and the uricosuric response elicited by probenecid. These data suggest an impaired tubular secretion of urate in most patients with gout that is not normalized by decreasing serum urate levels. The impaired tubular transport of urate may contribute to increased serum urate in primary gout.

Uric acid excretion in healthy subjects: a nomogram to assess the mechanisms underlying purine metabolic disorders

The reference range for urinary uric acid excretion has not been precisely defined. Different urinary variables have been proposed to determine the renal contribution to increased or decreased serum urate concentrations. We examined which urinary variable best indicates uric acid excretion over a wide range of serum urate concentrations. Purine metabolism was studied in 10 healthy male subjects (aged 26-58 years) both at their endogenous normal serum urate levels (normouricemic state) and after the oral administration of allopurinol (300 mg/24 h for 5 days) and ribonucleic acid (4 g/8 h for 4 days) to decrease (hypouricemic state) and increase (hyperuricemic state) serum urate concentrations, respectively. The results from patients with several conditions known to affect uric acid synthesis and/or the renal excretion of uric acid were used to validate a constructed nomogram. Over a wide range of mean serum urate levels (from 2.7 to 9.5 mg/dL) and mean 24-hour urinary uric acid excretion (171 to 1368 mg/[24 h 1.73 m(2)]), the highest correlation coefficient between serum urate and uric acid excretion was obtained for the 24-hour uric acid determination (r = 0.928; P < .001). The constructed nomogram allowed the definition of the mechanism underlying hyperuricemia and hypouricemia in patients with a myriad of diseases known to affect purine metabolism. The urinary variable that best correlates with a wide range of serum urate concentrations is 24-hour urinary uric acid excretion. The constructed nomogram allows the identification of the kidney contribution to a given purine metabolic abnormality.

Familial juvenile hyperuricaemic nephropathy (FJHN): linkage analysis in 15 families, physical and transcriptional characterisation of the FJHN critical region on chromosome 16p11.2 and the analysis of seven candidate genes

Familial juvenile hyperuricaemic nephropathy (FJHN) is an autosomal dominant renal disease characterised by juvenile onset of hyperuricaemia, gouty arthritis, and progressive renal failure at an early age. Recent studies in four kindreds showed linkage of a gene for FJHN to the same genomic interval on chromosome 16p11.2, where the gene for the phenotypically similar medullary cystic disease type 2 (MCKD2) has been localised. In this study we performed linkage analysis in additional 15 FJHN families. Linkage of FJHN to 16p11.2 was confirmed in six families, which suggests that, in a large proportion of FJHN kindreds, the disease is likely to be caused by a gene or genes located outside of 16p11.2. Haplotype analysis of the new and previously analysed families provided two non-overlapping critical regions on 16p11.2–FJHN1, delimited by markers D16S499-D16S3036 and FJHN2, delimited by markers D16S412-D16S3116. Considering MCKD2 to be a distinct molecular entity, the analysis suggests that as many as three kidney disease genes may be located in close proximity on 16p11.2. From genomic databases we compiled integrated physical and transcription maps of whole critical genomic region in which 45 known genes and 129 predicted loci have been localised. We selected, analysed and found no pathogenic mutations in seven candidate genes. The linkage and haplotype analysis reported here demonstrates the genetic heterogeneity of FJHN. The report of integrated physical and mostly in-silico predicted transcription maps of the FJHN critical region provides a basis for precise experimental annotation of the current transcript map, which is essential for final identification of the FJHN gene(s).

Comparison of single-pill strategies first line in hypertension: perindopril/amlodipine versus valsartan/amlodipine.

Objectives: An international double-blind, parallel-group, randomized controlled trial was performed to determine the efficacy and safety of a new first-line strategy in mild to moderate hypertension based on a single-pill combination of perindopril/amlodipine versus a validated stepped-care strategy (initiation with valsartan monotherapy, up-titrating to valsartan/amlodipine after 2 months). Methods: At inclusion, patients received perindopril/amlodipine 3.5/2.5u200amg or valsartan 80u200amg. At 1, 2, and 3 months, patients were up-titrated if they had uncontrolled hypertension (≥140/90u200ammHg). The up-titration steps were: perindopril/amlodipine 7/5u200amg, 14/10u200amg, and 14/10u200amg + indapamide sustained release 1.5u200amg; or valsartan 160u200amg, valsartan/amlodipine 160/5u200amg, and 160/10u200amg. The two groups were similar at baseline (55.5 years, 53% men, blood pressure 163.5/100.2u200ammHg); 881 perindopril/amlodipine and 876u200avalsartan/amlodipine patients were analyzed for efficacy. Results: After 1 month, the rate of controlled hypertension was 33% with perindopril/amlodipine versus 27% with valsartan/amlodipine (estimate of difference, +6.1%; Pu200a=u200a0.005); this between-strategy difference remained significant at every visit (Pu200a<u200a0.05). After 3 months, blood pressure was 137.8u200a±u200a12.4/83.3u200a±u200a8.7 and 139.7u200a±u200a13.3/84.8u200a±u200a9.0u200ammHg, respectively, with greater reductions from baseline with perindopril/amlodipine (primary endpoint −2.0/−1.5u200ammHg; both Pu200a<u200a0.001). Similar results were observed at all other visits (all Pu200a⩽u200a0.001). The safety of the two strategies was equivalent. Conclusions: The three-step strategy of initiation with single-pill perindopril/amlodipine produces greater reductions in blood pressure, and better and quicker rates of control of hypertension. This can be expected to be associated with benefits beyond blood pressure control, notably improved compliance and better cardioprotection.