GCH1 mutation and clinical study of Chinese patients with dopa-responsive dystonia.

Dopa-responsive dystonia (DRD) is typically caused by heterozygous mutations in GTP cyclohydrolase 1 gene (GCH1). Our aim was to investigate the clinical and genetic features of Chinese DRD patients. We analyzed a cohort of Chinese DRD patients' clinical data. Mutation of the GCH1 gene was screened by direct sequencing. Additionally, multiplex ligation-dependent probe amplification (MLPA) assay targeting the GCH1 and the TH gene to evaluate large exon deletion or duplicate mutation of the genes were performed in point mutation-negative patients. Ten sporadic DRD patients and two pedigrees including six patients were included in the study. The onset age ranged from 3 to 15 years old. All patients initially presented with walking problems due to lower limb dystonia. The delay between onset and diagnosis ranged from 1 to 42 years old. The symptoms were completely or near-completely abolished with low dose levodopa treatment (dosages ranged from 25 mg to 400 mg/day). Direct sequencing in 14 patients found two known mutations (Gly203Arg in exon 5 in four unrelated patients and Met102Lys in exon 1 in one patient) and one new mutation (Thr186Ile mutation in exon 5 in two unrelated pedigrees). A heterozygous exon 2 deletion in the GCH1 gene was found in one of three point mutation-negative patients by MLPA analysis. Our clinical findings in DRD patients were consistent with other studies. GCH1 gene mutations were quite common in Chinese patients. MPLA should be performed in routine deletion analysis of GCH1 in point mutation-negative DRD patients.

Trinucleotide expansions in the SCA7 gene in a large family with spinocerebellar ataxia and craniocervical dystonia.

Spinocerebellar ataxia type 7 is a rare autosomal dominant cerebellar ataxia (ADCA). Herein, we describe the molecular and clinical findings in patients within six generations of a large Chinese family with spinocerebellar ataxia. To identify the genetic cause(s), 4 affected patients and 26 asymptomatic relatives were recruited for the study. Molecular screening of the SCA1 and SCA7 genes was carried out by subcloning and direct PCR-sequencing methods. Both neurological and ophthalmic examinations were performed to investigate the clinical characteristics of the disease. The patients had typical cerebellar ataxia, achromatopsia and macular degeneration, and displayed a rare phenotype manifesting as a combination of cerebellar ataxia and craniocervical dystonia. Mutational analysis of the SCA7 genes demonstrated expanded CAG-repeats in the four patients. In conclusion, we identified expanded CAG-repeats in the SCA7 gene within members of a large Chinese family with spinocerebellar ataxia. The defined phenotypic characteristics of the patients may be helpful for clinical diagnosis and genetic typing of new patients.

Incidence of tardive dyskinesia and tardive dystonia in African Caribbean patients on long-term antipsychotic treatment: the Curaçao extrapyramidal syndromes study V.

OBJECTIVE: Tardive dyskinesia (TD) and tardive dystonia (TDt) syndromes represent severe side effects of first-generation antipsychotics (FGAs). Although second-generation antipsychotics (SGAs) confer a lower risk for tardive syndromes, many patients continue to use FGAs alone or in combination with SGAs. Some patients remain free of TD or TDt even after many years of antipsychotic treatment with predominantly FGAs. Do these patients remain at risk for TD or TDt and, consequently, should a switch to SGAs be considered? A longitudinal cohort study in patients on long-term antipsychotic treatment may answer this question. METHOD: A 9-year cohort study (1992-2001) was conducted of the whole, mostly chronic, psychiatric inpatient population on the Caribbean island of Curaçao (N = 194). Almost all patients (95%) were of African Carribean origin. TD and TDt were assessed (1 baseline, 6 follow-ups) with the Abnormal Involuntary Movement Scale and the Fahn-Marsden rating scale, respectively. New cases of TD or TDt were diagnosed if they fulfilled the criteria at 2 successive follow-up visits. RESULTS: In patients with a mean antipsychotic use of approximately 18 years, the yearly incidence rates of TD and TDt were 10.2% (95% CI = 7.7 to 13.5) and 0.7% (95% CI = 0.4 to 1.5), respectively. The severity of TD was strongly associated with the severity of TDt (beta = 0.08, 95% CI = 0.03 to 0.14) and vice versa (beta = 0.10, 95% CI = 0.03 to 0.16). TD severity was positively associated with age and akathisia but negatively associated with parkinsonism. CONCLUSIONS: Patients who are free of TD after many years of antipsychotic treatment still have a considerable risk for TD. Switching to an SGA may be warranted. The risk for incident TDt in this group was very low.

[TH gene mutation in Chinese patients with autosomal recessive dopa-responsive dystonia].

OBJECTIVE: To explore the mutation of tyrosine hydroxylase(TH) gene in Chinese patients with autosomal recessive(AR) dopa-responsive dystonia(DRD) and to lay a solid basis for gene diagnosis of AR-DRD in China. METHODS: Mutation analysis of TH gene was performed in 5 probands with AR-DRD and 2 sporadic patients with DRD by use of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) combining DNA direct sequencing. RESULTS: The PCR-SSCP analysis and DNA direct sequencing following PCR revealed no mutation in all the 14 exons of TH gene. CONCLUSION: The mutation rate of TH gene in Chinese patients with AR-DRD is low, hence suggesting the genetic heterogeneity and a new locus for AR-DRD.

Dopa-responsive dystonia and Tourette syndrome in a large Danish family.

BACKGROUND: Guanosine triphosphate cyclohydrolase I (GTPCH) catalyzes the first step in the synthesis of tetrahydrobiopterin (BH4). Autosomal dominantly inherited defects in the GTPCH gene (GCH1) cause a form of dystonia that is responsive to treatment with levodopa (dopa-responsive dystonia [DRD]). OBJECTIVE: To investigate molecular and clinical aspects of DRD in a large Danish family. METHODS: For analysis of the GCH1 gene, a mutation-scanning method based on denaturing gradient gel electrophoresis (DGGE) was used. A novel mutation, X251R, was identified in the GCH1 gene of 2 distantly related Danish patients with DRD, one of whom also had Tourette syndrome (TS). Thirty-five additional family members were investigated for this mutation, and 16 of them underwent clinical neurological examination. RESULTS: A total of 18 patients were heterozygous for the X251R allele, 16 of whom had neurological complaints spanning from very mild parkinsonism to severe invalidism due to dystonia. Of 13 symptomatic heterozygotes who had been neurologically examined, 10 had signs of dystonia or parkinsonism. Sixteen of the heterozygotes were treated with levodopa, and 13 reported a treatment benefit. Three of the symptomatic heterozygotes had signs of TS. CONCLUSIONS: This study confirms the large variability in DRD symptoms and emphasizes the usefulness of molecular analysis for diagnosis and treatment of DRD. The presence of TS is suggested to be coincidental, though the development of TS-like symptoms due to mutations in GCH1 cannot be excluded.

Genetic testing for early-onset torsion dystonia (DYT1): introduction of a simple screening method, experiences from testing of a large patient cohort, and ethical aspects.

Early-onset, generalized primary torsion dystonia (PTD) is an autosomal dominantly inherited disorder, characterized by involuntary movements and abnormal postures. The majority of cases are caused by a 3-bp deletion in the DYT1 gene on chromosome 9q34 that allows for specific genetic testing. We developed a simple, reliable, and cost-effective, PCR-based screening method for this mutation. Testing results from a cohort of 550 cases, including patients with different forms of dystonia and unclassified movement disorders, revealed that 72.2% of the patients with typical early-onset generalized PTD carried the GAG deletion in the DYT1 gene. Among 300 cases with late-onset focal/segmental dystonia, only 3 patients tested positive for the GAG deletion whereas 12.8% of the patients with an unclassified movement disorder were GAG positive. Our results confirm a genotype/phenotype correlation in early-onset PTD and show that application of strict clinical criteria leads to accurate prediction of carrier status in more than two-thirds of patients with this type of dystonia. Currently, we suggest that testing be recommended in individuals with age of onset of dystonia below 30 years and/or a positive family history of early-onset PTD. Testing is not recommended in patients with onset of symptoms after 30 years or in asymptomatic individuals under the age of 18.

Dystonia in Ashkenazi Jews: clinical characterization of a founder mutation.

A gene (DYT1) for idiopathic torsion dystonia maps to chromosome 9q34 in Ashkenazi Jewish families with early onset of symptoms. Further, there is linkage disequilibrium between DYT1 and a particular haplotype of alleles at 9q34 loci in this population. This implies that a large proportion of early-onset idiopathic torsion dystonia in Ashkenazi Jews is due to a founder mutation in DYT1. To characterize the phenotypic range of this mutation, we studied 174 Ashkenazi Jewish individuals affected with idiopathic torsion dystonia. We used GT(n) markers on chromosome 9q34 (D9S62, D9S63, and ASS) and classified individuals as having ("carriers"), not having ("noncarriers"), or being ambiguous with respect to a DYT1-associated haplotype. We assessed clinical features and found marked clinical differences between haplotype carriers and noncarriers. There were 90 carriers, 70 noncarriers, and 14 ambiguous individuals. The mean age at onset of symptoms was significantly lower in carriers than in noncarriers (12.5 +/- 8.2 vs 36.5 +/- 16.4 years). In 94% of carriers, symptoms began in a limb (arm or leg equally); rarely the disorder started in the neck (3.3%) or larynx (2.2%). In contrast, the neck, larynx, and other cranial muscles were the sites of onset in 79% of noncarriers; onset in the arms occurred in 21% and onset in the legs never occurred. Limb onset, leg involvement in the course of disease, and age at onset distinguished haplotype carriers from noncarriers with 90% accuracy. In conclusion, there are clinical differences between Ashkenazi Jewish individuals with idiopathic torsion dystonia who do or do not have a unique DYT1 mutation, as determined by a DYT1-associated haplotype of 9q34 alleles.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine beta-hydroxylase gene excluded in four subtypes of hereditary dystonia.

The hereditary dystonias include a clinically heterogeneous group of movement disorders varying in symptoms, age of onset, and drug responsiveness. Dopamine beta-hydroxylase (DBH), the enzyme that converts dopamine to norepinephrine, has been implicated in dystonia because of increased serum levels of DBH in some patients, the influence of catecholaminergic drugs on the human phenotypes, and altered norepinephrine levels in several brain regions in dystonia patients and in genetically dystonic rodents. In addition, markers linked to the dystonia gene in two ethnic groups map close to the DBH locus on human chromosome 9q34. Here we evaluate the inheritance of restriction fragment length polymorphisms near the DBH gene in families with four subtypes of hereditary dystonia: Jewish and non-Jewish, early onset, generalized idiopathic torsion dystonia (ITD); dopa-responsive dystonia; and myoclonic dystonia. In all families, obligate recombination events were observed between the DBH and dystonia genes, thus excluding the DBH gene as the primary defect.

Inheritance of idiopathic torsion dystonia among Ashkenazi Jews.

The mechanism(s) of inheritance of primary dystonia are unclear. An autosomal recessive form among Ashkenazi Jews and an autosomal dominant form among non-Jews have been proposed. However, the patterns of inheritance, particularly among Ashkenazim, are controversial. In this report we have reviewed the literature particularly as it pertains to the mode of inheritance among Ashkenazim. We also report the results of a pilot study of the families of 25 independently ascertained Ashkenazi probands with onset of primary dystonia before age 27 years. A total of 91/98 living first-degree relatives were examined; of these 91, 86 were greater than or equal to 8 years of age at time of examination and were included in our analysis. Overall, 14/86 (16.3%) of first-degree relatives were affected. We found 11.4% (4/35) of parents, 22.2% (8/36) of siblings, and 13.3% (2/15) of offspring were definitely affected. This finding of an approximately equal risk to parents, siblings, and offspring is consistent with autosomal dominant transmission with a minimum penetrance of 32.6%. Our findings do not support autosomal recessive or multifactorial inheritance.