Dopa-Responsive Dystonia in Han Chinese Patients: One Novel Heterozygous Mutation in GTP Cyclohydrolase 1 (GCH1) and Three Known Mutations in TH.

BACKGROUND This study aimed to clarify the diagnosis and expand the understanding of dopa-responsive dystonia (DRD). MATERIAL AND METHODS Relevant data from clinical diagnoses and genetic mutational analyses in 3 Han Chinese patients with sporadic DRD were collected and analyzed. Protein structure/function was predicted. RESULTS One novel mutation of c.679A>G (p.T227A) in GCH1 and 3 known mutations of c.457C>T (p.R153X), c.739G>A (p.G247S), and c.698G>A (p.R227H) in tyrosine hydroxylase (TH) have been found and predicted to be damaging or deleterious. All of the mutations were localized in conserved sequences. The iterative threading assembly refinement (I-TASSER) server generated three-dimensional (3D) atomic models based on protein sequences from the novel nonsense mutation of c.679A>G (p.T227A) in GCH1, which showed that residue 227 was located in the GCH1 active site. CONCLUSIONS Patients carrying different non-synonymous variants had remarkable variation in clinical phenotype. This study expands the spectrum of genotypes and phenotypes of DRD in the Han Chinese ethnicity, provides new insights into the molecular mechanism of DRD, and helps the diagnosis and treatment of DRD.

Simultaneous measurement of monoamine metabolites and 5-methyltetrahydrofolate in the cerebrospinal fluid of children.

BACKGROUND: We describe a new method for simultaneous measurement of monoamine metabolites (3-O-methyldopa [3-OMD], 3-methoxy-4-hydroxyphenylethyleneglycol [MHPG], 5-hydroxyindoleacetic acid [5-HIAA], and homovanillic acid [HVA]) and 5-methyltetrahydrofolate (5-MTHF) and its use on cerebrospinal fluid (CSF) samples from pediatric patients. METHODS: Monoamine metabolites and 5-MTHF were measured by high-performance liquid chromatography with fluorescence detection. CSF samples were prospectively collected from children according to a standardized collection protocol in which the first 1-ml fraction was used for analysis. RESULTS: Monoamine metabolites and 5-MTHF were separated within 10min. They showed linearity from the limit of detection to 1024nmol/l. The limit of quantification of each metabolite was sufficiently low for the CSF sample assay. In 42 CSF samples after excluding cases with possibly altered neurotransmitter profiles, the concentrations of 3-OMD, MHPG, 5-HIAA, HVA, and 5-MTHF showed significant age dependence and their ranges were comparable with the reference values in the literature. The metabolite profiles of aromatic l-amino acid decarboxylase deficiency, Segawa disease, and folate receptor α defect by this method were compatible with those in the literature. CONCLUSIONS: This method is a simple means of measuring CSF monoamine metabolites and 5-MTHF, and is especially useful for laboratories not equipped with electrochemical detectors.

Cerebrospinal fluid synaptic proteins as useful biomarkers in tyrosine hydroxylase deficiency.

Tyrosine hydroxylase (TH) deficiency is an inborn error of dopamine biosynthesis and a cause of early parkinsonism. Two clinical phenotypes have been described. Type "B": early onset severe encephalopathy; type "A": later onset, less severe and better response to L-dopa. We aimed to study the expression of several key dopaminergic and gabaergic synaptic proteins in the cerebrospinal fluid (CSF) of a series of patients with TH deficiency and their possible relation with the clinical phenotype and response to L-DOPA. Dopamine transporter (DAT), D2-receptor and vesicular monoamine transporter (VMAT2) were measured in the CSF of 10 subjects with TH deficiency by Western blot analysis. In 3 patients, data of pre- and post-treatment with L-DOPA were available, and in one of them, GABA vesicular transporter was determined. Results were compared to an age-matched control population. The concentration of D2-receptors in CSF was significantly higher in patients with TH deficiency than in controls. Similarly, DAT and vesicular monoamine transporter type 2 were up-regulated. Studies performed before L-DOPA, and on L-DOPA therapy showed a paradoxical response with D2 receptor expression increase as L-Dopa doses and homovanillic concentration gradually raised in a B phenotype patient. The opposite results were found in two patients with A phenotype. However, this is a very small sample, and further studies are needed to conclude robust differences between phenotypes. Synaptic proteins are detectable in the CSF and their quantification can be useful for understanding the pathophysiology of neurotransmitter defects and potentially to adjust and personalize treatments in the future.

Novel mutations in the guanosine triphosphate cyclohydrolase 1 gene associated with DYT5 dystonia.

OBJECTIVES: To better understand the relationship between mutation of the guanosine triphosphate cyclohydrolase I (GCH1) gene and the etiology of DYT5 dystonia and to accumulate data on the mutation in the Japanese population for genetic diagnosis of the disease. SETTING: Japanese population. Patients Eight Japanese patients with suspected DYT5 dystonia were analyzed. Intervention Direct genomic sequencing of 6 exons of GCH1 was performed. MAIN OUTCOME MEASURES: For patients who did not exhibit any abnormality in the sequence analysis, the possibility of exon deletions was examined. In cases for which cerebrospinal fluid was available, the concentrations of neopterin and biopterin were measured as an index of GCH1 enzyme activity. RESULTS: In 2 patients, we found a new T106I mutation in exon 1 of GCH1, a position involved in the helix-turn-helix structure of the enzyme. In the third patient, we found a new mutation (a 15-base pair nucleotide deletion) in exon 5 that may cause a frameshift involving the active site. In the fourth patient, we detected a known nucleotide G>A substitution in the splice site of intron 5, which has been reported to produce exon 5-skipped messenger RNA. The concentrations of both neopterin and biopterin in the cerebrospinal fluid of the third and fourth patients were markedly lower than the normal range, indicating that the GCH1 enzyme was functionally abnormal in these mutations. Gene dosage analysis showed that the fifth patient had a deletion of both exon 3 and exon 4, whereas the sixth patient had a deletion of exon 3. CONCLUSIONS: We found several novel, as well as known, GCH1 mutations in Japanese patients with DYT5 dystonia. In some of them, the GCH1 enzyme activity was proved to be impaired.

Mistaken diagnosis of psychogenic gait disorder in a man with status cataplecticus ("limp man syndrome").

We report on a 45-year-old man with a history of multiple psychiatric admissions for a gait disorder and episodic weakness thought to be psychogenic who was subsequently diagnosed with status cataplecticus due to narcolepsy. The gait difficulties resolved with venlafaxine. This case demonstrates that status cataplecticus can be misdiagnosed as a psychogenic gait disorder.

Infantile Parkinsonism-dystonia and elevated dopamine metabolites in CSF.

Two girls and one boy are described, with severe infantile parkinsonism-dystonia. This syndrome is usually caused by endogenous dopamine deficiency but in these patients was associated with elevated dopamine metabolites in CSF and an unusual eye movement disorder: ocular flutter together with saccade initiation failure. Pyramidal tract signs also emerged in the course of the disease in two patients. This combination of symptoms and biochemical findings suggests a unique pathogenic mechanism.

Phenotypic heterogeneity of dopa-responsive dystonia in monozygotic twins.

The clinical expression of dopa-responsive dystonia (DRD) was found to be different in a pair of affected monozygotic twins. An earlier onset was associated with a more disabling course of disease. Whereas monozygosity was genetically proven, the search for pathogenic mutations in the GTP-cyclohydrolase-1 gene was negative. The contribution of environmental factors appeared minimal. Intrafamilial variability of DRD phenotype may be related to yet unknown non-Mendelian epigenetic or proteomic factors.