Joubert syndrome and related disorders: spectrum of neuroimaging findings in 75 patients.
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ABSTRACT:
SUBMITTER: Poretti A
PROVIDER: S-EPMC7964342 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Joubert syndrome (JS) is a rare autosomal recessive (AR), neurological condition characterized by dysgenesis of the cerebellar vermis with the radiological hallmark of molar tooth sign, oculomotor apraxia, recurrent hyperventilation and intellectual disability. Most cases display a broad spectrum of additional features, including polydactyly, retinal dystrophy and renal abnormalities, which define different subtypes of JS-related disorders (JSRDs). To date, 23 genes have been shown to cause JSRDs, and although most of the identified genes encode proteins involved in cilia function or assembly, the molecular mechanisms associated with ciliary signaling remain enigmatic. Arab populations are ethnically diverse with high levels of consanguinity (20-60%) and a high prevalence of AR disorders. In addition, isolated communities with very-high levels of inbreeding and founder mutations are common. In this article, we review the 70 families reported thus far with JS and JSRDs that have been studied at the molecular level from all the Arabic countries and compile the mutations found. We show that JS and the related JSRDs are genetically heterogeneous in Arabs, with 53 mutations in 15 genes. Thirteen of these mutations are potentially founder mutations for the region.
| S-EPMC4785524 | biostudies-literature
Project description:[This corrects the article DOI: 10.1038/hgv.2014.20.].
| S-EPMC4785561 | biostudies-other
Project description:Joubert syndrome (JS) and related disorders (JSRD) are a group of developmental delay/multiple congenital anomalies syndromes in which the obligatory hallmark is the molar tooth sign (MTS), a complex midbrain-hindbrain malformation visible on brain imaging, first recognized in JS. Estimates of the incidence of JSRD range between 1/80,000 and 1/100,000 live births, although these figures may represent an underestimate. The neurological features of JSRD include hypotonia, ataxia, developmental delay, intellectual disability, abnormal eye movements, and neonatal breathing dysregulation. These may be associated with multiorgan involvement, mainly retinal dystrophy, nephronophthisis, hepatic fibrosis and polydactyly, with both inter- and intra-familial variability. JSRD are classified in six phenotypic subgroups: Pure JS; JS with ocular defect; JS with renal defect; JS with oculorenal defects; JS with hepatic defect; JS with orofaciodigital defects. With the exception of rare X-linked recessive cases, JSRD follow autosomal recessive inheritance and are genetically heterogeneous. Ten causative genes have been identified to date, all encoding for proteins of the primary cilium or the centrosome, making JSRD part of an expanding group of diseases called "ciliopathies". Mutational analysis of causative genes is available in few laboratories worldwide on a diagnostic or research basis. Differential diagnosis must consider in particular the other ciliopathies (such as nephronophthisis and Senior-Loken syndrome), distinct cerebellar and brainstem congenital defects and disorders with cerebro-oculo-renal manifestations. Recurrence risk is 25% in most families, although X-linked inheritance should also be considered. The identification of the molecular defect in couples at risk allows early prenatal genetic testing, whereas fetal brain neuroimaging may remain uninformative until the end of the second trimester of pregnancy. Detection of the MTS should be followed by a diagnostic protocol to assess multiorgan involvement. Optimal management requires a multidisciplinary approach, with particular attention to respiratory and feeding problems in neonates and infants. Cognitive and behavioral assessments are also recommended to provide young patients with adequate neuropsychological support and rehabilitation. After the first months of life, global prognosis varies considerably among JSRD subgroups, depending on the extent and severity of organ involvement.
| S-EPMC2913941 | biostudies-literature
Project description:Since the identification of Fetal Alcohol Syndrome over 40 years ago, much has been learned about the detrimental effects of prenatal alcohol exposure on the developing brain. This review highlights recent neuroimaging studies, within the context of previous work. Structural magnetic resonance imaging has described morphological differences in the brain and their relationships to cognitive deficits and measures of facial dysmorphology. Diffusion tensor imaging has elaborated on the relationship between white matter microstructure and behavior. Atypical neuromaturation across childhood and adolescence has been observed in longitudinal neuroimaging studies. Functional imaging has revealed differences in neural activation patterns underlying sensory processing, cognition and behavioral deficits. A recent functional connectivity analysis demonstrates reductions in global network efficiency. Despite this progress much remains unknown about the impact of prenatal alcohol exposure on the brain, and continued research efforts are essential.
| S-EPMC4207054 | biostudies-literature
Project description:Joubert syndrome and related disorders (JSRD) are clinically and genetically heterogeneous ciliopathies sharing a peculiar midbrain-hindbrain malformation known as the 'molar tooth sign'. To date, 19 causative genes have been identified, all coding for proteins of the primary cilium. There is clinical and genetic overlap with other ciliopathies, in particular with Meckel syndrome (MKS), that is allelic to JSRD at nine distinct loci. We previously identified the INPP5E gene as causative of JSRD in seven families linked to the JBTS1 locus, yet the phenotypic spectrum and prevalence of INPP5E mutations in JSRD and MKS remain largely unknown. To address this issue, we performed INPP5E mutation analysis in 483 probands, including 408 JSRD patients representative of all clinical subgroups and 75 MKS fetuses. We identified 12 different mutations in 17 probands from 11 JSRD families, with an overall 2.7% mutation frequency among JSRD. The most common clinical presentation among mutated families (7/11, 64%) was Joubert syndrome with ocular involvement (either progressive retinopathy and/or colobomas), while the remaining cases had pure JS. Kidney, liver and skeletal involvement were not observed. None of the MKS fetuses carried INPP5E mutations, indicating that the two ciliopathies are not allelic at this locus.
| S-EPMC3778343 | biostudies-literature
Project description:Joubert syndrome (JBTS; OMIM 213300) is a rare, autosomal recessive disorder characterized by a specific congenital malformation of the hindbrain and a broad spectrum of other phenotypic findings that is now known to be caused by defects in the structure and/or function of the primary cilium. The complex hindbrain malformation that is characteristic of JBTS can be identified on axial magnetic resonance imaging and is known as the molar tooth sign (MTS); other diagnostic criteria include intellectual disability, hypotonia, and often, abnormal respiratory pattern and/or abnormal eye movements. In addition, a broad spectrum of other anomalies characterize Joubert syndrome and related disorders (JSRD), and may include retinal dystrophy, ocular coloboma, oral frenulae and tongue tumors, polydactyly, cystic renal disease (including cystic dysplasia or juvenile nephronophthisis), and congenital hepatic fibrosis. The clinical course can be variable, but most children with this condition survive infancy to reach adulthood. At least eight genes cause JSRD, with some genotype-phenotype correlations emerging, including the association between mutations in the MKS3 gene and hepatic fibrosis characteristic of the JSRD subtype known as COACH syndrome. Several of the causative genes for JSRD are implicated in other ciliary disorders, such as juvenile nephronophthisis and Meckel syndrome, illustrating the close association between these conditions and their overlapping clinical features that reflect a shared etiology involving the primary cilium.
| S-EPMC2797758 | biostudies-literature
Project description:Joubert syndrome and related disorders (JSRD; ORPHA 140874) is a complex set of neurodevelopmental disorders with multiple organ involvement. JSRD is a type of ciliopathy which is caused by the presence of defective primary cilia in an individual. JSRD is commonly inherited in an autosomal recessive pattern, and more than 23 genes are known to be associated with JSRD. We report a novel homozygous mutation identified in the INPP5E gene, c.1303C>T, which leads to a change of an amino acid from arginine to tryptophan at residue 435 in the protein chain. In silico analysis indicates that p.Arg435Trp substitution affects the functionality of the protein product of the gene. Our result adds to the growing body of evidences that underlines the clinical utility of next-generation sequencing in the diagnosis of a genetic disorder when clinical features are inconclusive.
| S-EPMC5701266 | biostudies-literature
Project description:We describe two brothers with Joubert syndrome (JS). JS diagnosis was made on the basis of neurological findings and the presence of the characteristic "molar tooth sign", which was subsequently confirmed by magnetic resonance imaging. Both brothers demonstrated ptosis, hypotropia, exotropia, and horizontal pendular nystagmus. The younger brother had mild chorioretinal discoloration at the peripapillary region in both eyes, and a small coloboma at the inferior region of his right optic disc. The elder brother had coloboma in his right eye and a colobomatous optic disc in his left eye. Optical coherence tomography showed that the foveal architecture was preserved in both patients. We discuss the ocular findings, including those from optical coherence tomography, in JS, which has recently been recognized as ciliopathy.
| S-EPMC3896311 | biostudies-other
Project description:Emanuel syndrome is a rare inherited chromosomal abnormality caused by an unbalanced translocation of chromosomes 11 and 22. Clinically, Emanuel syndrome is characterized by a wide spectrum of congenital anomalies, dysmorphisms, and developmental disability often confused with other similar syndromes. Outside of genetic testing, diagnosis remains challenging and current literature on typical radiologic findings is limited. We present classic neuroimaging findings of Emanuel syndrome consistent with prior literature including microcephaly, microretrognathia, external auditory canal stenosis, and cleft palate; and also introduce the additional maxillofacial anomaly of dysplastic middle ear ossicles, to our knowledge not previously described in the literature. Recognition of findings leading to earlier diagnosis of Emanuel syndrome may improve outcomes and quality of life for patients and their families.
| S-EPMC7060007 | biostudies-literature
Project description:ObjectivesTo determine the frequency of KCNQ2 mutations in patients with neonatal epileptic encephalopathy (NEE), and to expand the phenotypic spectrum of KCNQ2 epileptic encephalopathy.MethodsEighty-four patients with unexplained NEE were screened for KCNQ2 mutations using classic Sanger sequencing. Clinical data of 6 additional patients with KCNQ2 mutations detected by gene panel were collected. Detailed phenotyping was performed with particular attention to seizure frequency, cognitive outcome, and video-EEG.ResultsIn the cohort, we identified 9 different heterozygous de novo KCNQ2 missense mutations in 11 of 84 patients (13%). Two of 6 missense mutations detected by gene panel were recurrent and present in patients of the cohort. Seizures at onset typically consisted of tonic posturing often associated with focal clonic jerking, and were accompanied by apnea with desaturation. One patient diagnosed by gene panel had seizure onset at the age of 5 months. Based on seizure frequency at onset and cognitive outcome, we delineated 3 clinical subgroups, expanding the spectrum of KCNQ2 encephalopathy to patients with moderate intellectual disability and/or infrequent seizures at onset. Recurrent mutations lead to relatively homogenous phenotypes. One patient responded favorably to retigabine; 5 patients had a good response to carbamazepine. In 6 patients, seizures with bradycardia were recorded. One patient died of probable sudden unexpected death in epilepsy.ConclusionKCNQ2 mutations cause approximately 13% of unexplained NEE. Patients present with a wide spectrum of severity and, although rare, infantile epilepsy onset is possible.
| S-EPMC3812107 | biostudies-literature