Karine Nguyen

Exhaustive analysis of BH4 and dopamine biosynthesis genes in patients with Dopa-responsive dystonia

Dopa-responsive dystonia is a childhood-onset dystonic disorder, characterized by a dramatic response to low dose of L-Dopa. Dopa-responsive dystonia is mostly caused by autosomal dominant mutations in the GCH1 gene (GTP cyclohydrolase1) and more rarely by autosomal recessive mutations in the TH (tyrosine hydroxylase) or SPR (sepiapterin reductase) genes. In addition, mutations in the PARK2 gene (parkin) which causes autosomal recessive juvenile parkinsonism may present as Dopa-responsive dystonia. In order to evaluate the relative frequency of the mutations in these genes, but also in the genes involved in the biosynthesis and recycling of BH4, and to evaluate the associated clinical spectrum, we have studied a large series of index patients (n = 64) with Dopa-responsive dystonia, in whom dystonia improved by at least 50% after L-Dopa treatment. Fifty seven of these patients were classified as pure Dopa-responsive dystonia and seven as Dopa-responsive dystonia-plus syndromes. All patients were screened for point mutations and large rearrangements in the GCH1 gene, followed by sequencing of the TH and SPR genes, then PTS (pyruvoyl tetrahydropterin synthase), PCBD (pterin-4a-carbinolamine dehydratase), QDPR (dihydropteridin reductase) and PARK2 (parkin) genes. We identified 34 different heterozygous point mutations in 40 patients, and six different large deletions in seven patients in the GCH1 gene. Except for one patient with mental retardation and a large deletion of 2.3 Mb encompassing 10 genes, all patients had stereotyped clinical features, characterized by pure Dopa-responsive dystonia with onset in the lower limbs and an excellent response to low doses of L-Dopa. Dystonia started in the first decade of life in 40 patients (85%) and before the age of 1 year in one patient (2.2%). Three of the 17 negative GCH1 patients had mutations in the TH gene, two in the SPR gene and one in the PARK2 gene. No mutations in the three genes involved in the biosynthesis and recycling of BH4 were identified. The clinical presentations of patients with mutations in TH and SPR genes were strikingly more complex, characterized by mental retardation, oculogyric crises and parkinsonism and they were all classified as Dopa-responsive dystonia-plus syndromes. Patient with mutation in the PARK2 gene had Dopa-responsive dystonia with a good improvement with L-Dopa, similar to Dopa-responsive dystonia secondary to GCH1 mutations. Although the yield of mutations exceeds 80% in pure Dopa-responsive dystonia and Dopa-responsive dystonia-plus syndromes groups, the genes involved are clearly different: GCH1 in the former and TH and SPR in the later.

Morbidity and mortality from ataxia-telangiectasia are associated with ATM genotype

BACKGROUND Ataxia-telangiectasia (A-T) is a rare genetic disease caused by germline biallelic mutations in the ataxia-telangiectasia mutated gene (ATM) that result in partial or complete loss of ATM expression or activity. The course of the disease is characterized by neurologic manifestations, infections, and cancers. OBJECTIVE We studied A-T progression and investigated whether manifestations were associated with the ATM genotype. METHODS We performed a retrospective cohort study in France of 240 patients with A-T born from 1954 to 2005 and analyzed ATM mutations in 184 patients, along with neurologic manifestations, infections, and cancers. RESULTS Among patients with A-T, the Kaplan-Meier 20-year survival rate was 53.4%; the prognosis for these patients has not changed since 1954. Life expectancy was lower among patients with mutations in ATM that caused total loss of expression or function of the gene product (null mutations) compared with that seen in patients with hypomorphic mutations because of earlier onset of cancer (mainly hematologic malignancies). Cancer (hazard ratio, 2.7; 95% CI, 1.6-4.5) and respiratory tract infections (hazard ratio, 2.3; 95% CI, 1.4-3.8) were independently associated with mortality. Cancer (hazard ratio, 5.8; 95% CI, 2.9-11.6) was a major risk factor for mortality among patients with null mutations, whereas respiratory tract infections (hazard ratio, 4.1; 95% CI, 1.8-9.1) were the leading cause of death among patients with hypomorphic mutations. CONCLUSION Morbidity and mortality among patients with A-T are associated with ATM genotype. This information could improve our prognostic ability and lead to adapted therapeutic strategies.

Quantitative assessment of the evolution of cerebellar signs in spinocerebellar ataxias

Responsive ataxia rating scales are essential for determining outcome measures in clinical trials.

New practical definitions for the diagnosis of autosomal recessive spastic ataxia of Charlevoix–Saguenay

Autosomal recessive spastic ataxia of Charlevoix–Saguenay (ARSACS) is caused by mutations in the SACS gene. SACS encodes sacsin, a protein whose function remains unknown, despite the description of numerous protein domains and the recent focus on its potential role in the regulation of mitochondrial physiology. This study aimed to identify new mutations in a large population of ataxic patients and to functionally analyze their cellular effects in the mitochondrial compartment.

Incidental findings on array comparative genomic hybridization: detection of carrier females of dystrophinopathy without any family history

Array comparative genomic hybridization (aCGH) has progressively replaced conventional karyotype in the diagnostic strategy of intellectual disability (ID) and congenital malformations. This technique increases not only the diagnostic rate but also the possibility of finding unexpected variants unrelated to the indication of referral, namely incidental findings. The incidental finding of copy number variants (CNVs) located in X‐linked genes in girls addresses the crucial question of genetic counseling in the family. We report here five cases of CNVs involving the dystrophin gene detected by aCGH in girls referred for developmental delay, without any family history of dystrophinopathy. The rearrangements included three in‐frame deletions; one maternally and two paternally inherited, and two frameshift duplications: one de novo and one from undetermined inheritance. In two cases, the deletion identified in a girl was transmitted by the asymptomatic father. In the case of the maternally inherited deletion, prenatal diagnosis of dystrophinopathy was proposed for an ongoing pregnancy, whereas the cause of developmental delay in the index case remained unknown. Through these cases, we discussed the challenges of genetic counseling in the family, regarding the predictive issues for male individuals at risk for a muscular dystrophy without precise knowledge of the clinical consequences of some CNVs in the DMD gene.

Parkinson's disease associated with 22q11.2 deletion: Clinical characteristics and response to treatment

BACKGROUND While it is known that 22q11.2 microdeletions (22q11.2-del) increase the risk of Parkinsons disease (PD), the characteristics of PD associated with 22q11.2-del have not been specifically explored. OBJECTIVE This report aimed to assess the clinical characteristics and treatment responses of PD patients with 22q11.2-del, and to describe any features that might lead neurologists to investigate the comorbidity. METHODS Nine PD patients (eight men, one woman) with 22q11.2-del were followed at seven centers of the French PD Expert Network (Ns-Park). RESULTS PD diagnosis was made before 22q11.2-del diagnosis in seven cases; their main characteristics were early onset (32-48 years) and good initial levodopa sensitivity, but with a course characterized by severe and early-onset levodopa-induced motor complications and psychiatric manifestations. Three patients received deep brain stimulation (DBS) that was effective. CONCLUSION Searching for 22q11.2-del in PD patients presenting with suggestive features is relevant as the clinical presentation is similar to idiopathic PD, but with other associated characteristics, including a severe evolution. Results with DBS are similar to those reported for idiopathic PD.

Syndrome oculodentodigital révélé par une paraparésie spastique progressive

Resume Le syndrome oculodentodigital (ODD) est un syndrome malformatif congenital rare d’origine genetique et de cause inconnue. Il associe de facon variable des signes oculaires (microphtalmie, microcornee), des anomalies dentaires (hypoplasie de l’email, edentation precoce) et des anomalies des extremites a type de syndactylie des 4 e et 5 e doigts. Une atteinte neurologique, le plus souvent a type de paraparesie spastique a ete rapportee dans plusieurs observations de syndrome ODD. L’heredite de ce syndrome est le plus souvent autosomique dominante. Cette observation rapporte le cas d’un patient atteint d’un syndrome ODD revele tardivement a l’âge adulte par une paraparesie spastique. Elle corrobore l’idee que le spectre du syndrome inclut l’atteinte neurologique et souligne le caractere tardif du diagnostic de ce syndrome revele par des manifestations neurologiques.

MCA/MR syndrome with hypocholesterolemia related to familial dominant hypobetalipoproteinemia

Recent reports have emphasized the role of cholesterol in vertebrate embryonic development. The RSH or so‐called Smith–Lemli–Opitz syndrome (SLOS) was the first multiple congenital anomalies/mental retardation syndrome related to a cholesterol synthesis disturbance. Familial hypobetalipoproteinemia is a well‐known dominantly inherited entity in which affected individuals usually are free of symptoms. We report on the unusual association of a malformation syndrome with mental retardation resembling SLOS and profound hypocholesterolemia related to familial hypobetalipoproteinemia. We discuss the possible causal relationship between the two conditions and the current understanding of the role of cholesterol in normal embryogenesis.

Typical features of Parkinson disease and diagnostic challenges with microdeletion 22q11.2

Objective To delineate the natural history, diagnosis, and treatment response of Parkinson disease (PD) in individuals with 22q11.2 deletion syndrome (22q11.2DS), and to determine if these patients differ from those with idiopathic PD. Methods In this international observational study, we characterized the clinical and neuroimaging features of 45 individuals with 22q11.2DS and PD (mean follow-up 7.5 ± 4.1 years). Results 22q11.2DS PD had a typical male excess (32 male, 71.1%), presentation and progression of hallmark motor symptoms, reduced striatal dopamine transporter binding with molecular imaging, and initial positive response to levodopa (93.3%). Mean age at motor symptom onset was relatively young (39.5 ± 8.5 years); 71.4% of cases had early-onset PD (<45 years). Despite having a similar age at onset, the diagnosis of PD was delayed in patients with a history of antipsychotic treatment compared with antipsychotic-naive patients (median 5 vs 1 year, p = 0.001). Preexisting psychotic disorders (24.5%) and mood or anxiety disorders (31.1%) were common, as were early dystonia (19.4%) and a history of seizures (33.3%). Conclusions Major clinical characteristics and response to standard treatments appear comparable in 22q11.2DS-associated PD to those in idiopathic PD, although the average age at onset is earlier. Importantly, treatment of preexisting psychotic illness may delay diagnosis of PD in 22q11.DS patients. An index of suspicion and vigilance for complex comorbidity may assist in identifying patients to prioritize for genetic testing.

Hypokalaemia and dysmorphia, is there a link?

A 15-year-old boy with quadriplegia and facial dysmorphia was referred to the emergency room. This was his first episode of tetraplegia. One maternal uncle had exhibited the same manifestation 20 years before. Blood test revealed severe hypokalaemia and mild hypocalcaemia. The clinical diagnosis revealed an Andersen–Tawil syndrome. Molecular tools allowed us to make the diagnosis of familial hypokalaemic periodic paralysis type 1 associated with a de novo 22q11.2 microdeletion syndrome. Our case report emphasizes the importance of molecular diagnosis in genetic diseases.