Molar Tooth Sign Research Articles

Biallelic TXNDC15 variants associated with Joubert syndrome-related molar tooth sign and forebrain malformation

Biallelic TXNDC15 variants associated with Joubert syndrome-related molar tooth sign and forebrain malformation

Joubert syndrome: a rare cause of hypotonia with developmental delay

Joubert syndrome is a rare autosomal recessive disorder. It is characterized by congenital ataxia, hypotonia, developmental delay, and at least one of the following features: neonatal respiratory disturbances and abnormal eye movements; including nystagmus and oculomotor apraxia. Molar tooth appearance is an essential finding for the diagnosis of Joubert syndrome. Here we presented a case of an 18-month-old male who presented with developmental delay and marked hypotonia. The main purposes of the case report were to highlight the benefit of a multidisciplinary rehabilitation team approach and describe the clinical features associated with Joubert syndrome. Brain magnetic resonance imaging showed a thick, elongated, and abnormally oriented superior cerebellar peduncle showing a molar tooth appearance with elongated bat-wing-shaped 4th ventricle and hypoplasia of the vermis suggestive of JS. Hypotonia during infancy and developmental delay with or without learning disability, associated with abnormal breathing patterns and abnormal eye movements (nystagmus) along with the radiological presence of a molar tooth sign on the brain MRI is an essential component to confirm the diagnosis.

Prenatal Diagnosis of Poretti-Boltshauser Syndrome - a Case Report of a Molar Tooth Sign Mimic.

We report the prenatal diagnosis of Poretti-Boltshauser Syndrome (PBS) in a 36-year-old primigravida woman. At 22 weeks and 6 days of gestation, fetal ultrasound revealed a normally shaped but hyperechogenic cerebellum with all supratentorial structures appearing normal. Differential diagnosis included cavernous hemangioma, capillary telangiectasia, and cerebellar hemorrhage. Subsequent fetal cerebral MRI showed diffuse bilateral cerebellar modifications, reduced cranio-caudal diameter of the vermis, and pathological elongation and thickening of the superior cerebellar peduncles indicative of the molar tooth sign. Amniocentesis and whole exome sequencing identified two heterozygous truncating variants in the LAMA1 gene: c.3099G > A (p.Trp1033Ter) and c.3699T > A (p.Tyr1233Ter), confirming PBS.) Following the diagnosis, the pregnancy was terminated at 23 weeks and 5 days. Post-mortem examination supported the MRI findings consistent with PBS. This case highlights the importance of integrating ultrasound, MRI, and genetic analysis for accurate prenatal diagnosis and emphasizes the molecular diversity associated with PBS, including the presence of molar tooth sign mimics and a novel c.3699T > A variant.

A Unique Case of Joubert Syndrome with Concurrent IgA Nephropathy and Nephronophthisis in an Adult Patient

A 30-year-old male born from a consanguineous marriage, with intellectual disability, developmental delay and Type 1 diabetes presented with polyuria and uremic symptoms. Physical examination revealed hypertension, retinitis pigmentosa, bilateral rotatory grade 3 nystagmus, eyelid droop, truncal obesity, acanthosis nigricans, and muscle hypotonia. Laboratory tests indicated kidney dysfunction. Magnetic resonance imaging of the brain showed the “molar tooth sign,” a hallmark of Joubert syndrome. The kidney biopsy highlighted features of IgA nephropathy, diabetic nephropathy, and nephronophthisis. Whole exome sequencing identified a homozygous nonsense variant in the AHI1 gene, known to cause Joubert syndrome 3. This case is unique due to its genetic proof of an AHI1 mutation causing Joubert syndrome in an Indian patient and the co-occurrence of IgA nephropathy with nephronophthisis.

Joubert syndrome caused by a TMEM67 mutation: Genotype-phenotype analysis

Joubert syndrome (JS), a rare neurodevelopmental disorder, is characterized by a unique midbrain- hindbrain malformation known as the molar tooth sign, a distinctive radiological feature. Among the myriad manifestations associated with JS, the most prevalent features encompass hypotonia, ataxia, developmental delay, intellectual disability, abnormal eye movements, and neonatal breathing abnormalities. To date, 29 genes have been identified as contributors to the development of JS. This study aimed to pinpoint a pathogenic variant in JS within an Iranian consanguineous pedigree. We employed whole-exome sequencing (WES) to pinpoint a potential pathogenic variant likely responsible for the condition in an 8-year-old male patient. The WES analysis successfully revealed a novel homozygous missense mutation (c.725A>T; p.Asn242Ile) within exon 8 (NM_153704.6) of the TMEM67 gene. Subsequent validation through Sanger sequencing confirmed the presence of the chr8-93780603A>T mutation. This study elucidated JS within an Iranian family, uncovering a new TMEM67 gene mutation through comprehensive genetic analysis. The identification of this mutation enhances our understanding of the genetic landscape of JS, contributing valuable insights for both clinical diagnosis and future research endeavors.

Open isthmus and lambda (Λ) sign of early Joubert syndrome: elucidating development of molar tooth sign.

Open isthmus and lambda (Λ) sign of early Joubert syndrome: elucidating development of molar tooth sign.

Ophthalmıc fındıngs ın Joubert syndrome 25: A case report

Joubert syndrome (JBTS; OMIM PS213300) is a rare autosomal recessive disease classified as a ciliopathy. The diagnosis of JBTS is based on three criteria: a characteristic brain imaging finding known as the “molar tooth sign,” hypotonia, and developmental delays. There is a well-defined ocular feature, including oculomotor apraxia, nystagmus, and strabismus. Retinal and optic nerve abnormalities have been reported. In a few cases where the genetic result is not specified, a papilledema-like appearance has been observed. To date, 35 mutations have been reported, with JBTS-25 being associated with the CEP104 gene. This report presents rare ocular findings in individuals with JBTS-25.

Joubert syndrome-derived induced pluripotent stem cells show altered neuronal differentiation in vitro.

Joubert syndrome (JS) is a recessively inherited congenital ataxia characterized by hypotonia, psychomotor delay, abnormal ocular movements, intellectual disability, and a peculiar cerebellar and brainstem malformation, the "molar tooth sign." Over 40 causative genes have been reported, all encoding for proteins implicated in the structure or functioning of the primary cilium, a subcellular organelle widely present in embryonic and adult tissues. In this paper, we developed an in vitro neuronal differentiation model using patient-derived induced pluripotent stem cells (iPSCs), to evaluate possible neurodevelopmental defects in JS. To this end, iPSCs from four JS patients harboring mutations in distinct JS genes (AHI1, CPLANE1, TMEM67, and CC2D2A) were differentiated alongside healthy control cells to obtain mid-hindbrain precursors and cerebellar granule cells. Differentiation was monitored over 31days through the detection of lineage-specific marker expression by qRT-PCR, immunofluorescence, and transcriptomics analysis. All JS patient-derived iPSCs, regardless of the mutant gene, showed a similar impairment to differentiate into mid-hindbrain and cerebellar granule cells when compared to healthy controls. In addition, analysis of primary cilium count and morphology showed notable ciliary defects in all differentiating JS patient-derived iPSCs compared to controls. These results confirm that patient-derived iPSCs are an accessible and relevant in vitro model to analyze cellular phenotypes connected to the presence of JS gene mutations in a neuronal context.

Case Report: An Adult Case of Poretti-Boltshauser Syndrome Diagnosed by Medical Checkup

This report describes an adult case of Poretti–Boltshauser syndrome (PTBHS) and with novel variants of LAMA1. A 65-year-old Japanese woman with cerebellar malformation identified during a medical checkup was referred to our hospital. Subsequently, neurological examination, brain imaging, and genetic investigation via whole-exome sequencing were performed. The patient presented with mild cerebellar ataxia and intellectual disability. Magnetic resonance imaging revealed cerebellar dysplasia and cysts and an absence of molar tooth sign. Genetic analysis revealed a novel homozygous variant of c.1711_1712del in LAMA1 (NM_005559.4). Most cases with PTBHS are reported in pediatric patients; however, our patient expressed a mild phenotype and was undiagnosed until her 60 s. These findings suggest that PTBHS should be considered in not only pediatric cerebellar dysplasia but also adult cerebellar ataxia with mild presentation.

Hydrocephalus associated with a molar tooth sign: A distinct subtype of Joubert syndrome.

Hydrocephalus is rarely described in Joubert-Boltshauser syndrome (JBTS). The aim of this study was to investigate whether this association is a chance occurrence or potentially signifies a new phenotypic subtype. The databases of Wolfson Medical Center, Sourasky Medical Center, and EB's personal collection were reviewed. Records from an additional family were obtained from RG. The patients' medical records, prenatal ultrasounds, and magnetic resonance imaging were assessed. In addition, we reviewed the medical literature for the association of ventriculomegaly/hydrocephalus (VM/HC) in JBTS. Only seven cases (from five families) were found with prenatal onset of VM/HC, diagnosed during the second trimester; three pregnancies were terminated, one was stillborn and three were born, of which one died within a week, and another died at the age of 6 years. Additional central nervous system findings included dysgenesis of the corpus callosum, delayed sulcation, polymicrogyria, and pachygyria. We found 16 publications describing 54 patients with JBTS and VM/HC: only five were diagnosed at birth and three were diagnosed prenatally. Hydrocephalus is extremely rare in JBTS. The recurrence of this association, reported in several publications in multiple family members, suggests that it might represent a new phenotypic subtype of JBTS possibly associated with specific genes or variants. Further genetic studies are needed to confirm this hypothesis. WHAT THIS PAPER ADDS: The association of fetal hydrocephalus with Joubert-Boltshauser syndrome (JBTS) is very rare but not a chance association. This association represents a new phenotypic subtype of JBTS possibly linked to specific genes or variants.

Hypopituitarism—A rare manifestation in Joubert syndrome: about 4 cases

<p>Joubert syndrome (JS) is a complex medical condition characterized by a pathognomonic midbrain-hindbrain malformation visible on brain imaging, which is known as the “molar tooth sign” (MTS). The presence of the MTS in the brain is the defining diagnostic criterion for JS. Individuals with JS commonly exhibit a developmental delay, hypotonia, and abnormal eye movements. In addition, neonatal breathing dysregulation is observed in about half of the cases. Midline brain defects associated with JS can lead to pituitary hormone abnormalities, thereby manifesting as multiple pituitary insufficiencies in the neonatal period, such as hypoglycemia and, in male patients, a micropenis with undescended testes. Although JS is a well-researched genetic condition, there is minimal information on the endocrinological aspects of JS. This manuscript aims to emphasize the spectrum of endocrinologic findings in JS through the retrospective evaluation of four cases characterized by combined pituitary dysfunctions, including secondary hypothyroidism, growth hormone deficiency, and panhypopituitarism. Highlighting these treatable aspects of JS is crucial, as continuous endocrinological monitoring can positively impact a patient's well-being, particularly in managing secondary adrenal and thyroid insufficiencies.</p>

A novel mutation of the RPGRIP1L gene in a Chinese boy with Joubert syndrome with oculorenal involvement

BackgroundJoubert syndrome (JS) is a rare genetically heterogeneous primary ciliopathy characterized by a pathognomonic cerebellar and brainstem malformation, the “molar tooth sign”, and variable organ involvement (such as eye, kidney, liver, and skeleton). Here, we present a case of JS in a Chinese boy.Case presentationAn 11-year-old Chinese boy presented with neonatal asphyxiation and hypoxia, strabismus, subsequent developmental delay, ataxia and end-stage kidney disease (ESKD). Routine blood tests showed severe anemia, increasing blood urea nitrogen and creatinine, elevated parathyroid hormone, hypocalcemia, hypokalemia and metabolic acidosis. Urine tests showed mild proteinuria. Ultrasound showed two small kidneys. Brain magnetic resonance imaging (MRI) showed dysplasia of the cerebellar vermis and extension of the upper cerebellar feet with the “molar tooth sign”. Genetic analysis showed novel compound heterozygous mutations in the RPGRIP1L gene [p.L447fs*7(p.Leu447fsTer7) and p.G908V (p.Gly908Val)].ConclusionIn the present study, we identified novel compound heterozygous mutations in the RPGRIP1L gene in a Chinese boy. The clinical and genetic findings of this study will expand the understanding of JS.

Phenotypic variability in Joubert syndrome is partially explained by ciliary pathophysiology.

Joubert syndrome (JS) arises from defects of primary cilia resulting in potential malformations of the brain, kidneys, eyes, liver, and limbs. Several of the 35+ genes associated with JS have recognized genotype/phenotype correlations, but most genes have not had enough reported individuals to draw meaningful conclusions. A PubMed literature review identified 688 individuals with JS across 32 genes and 112 publications to bolster known genotype/phenotype relationships and identify new correlations. All included patients had the "molar tooth sign" and a confirmed genetic diagnosis. Individuals were categorized by age, ethnicity, sex and the presence of developmental disability/intellectual disability, hypotonia, abnormal eye movements, ataxia, visual impairment, renal impairment, polydactyly, and liver abnormalities. Most genes demonstrated unique phenotypic profiles. Grouping proteins based on physiologic interactions established stronger phenotypic relationships that reflect known ciliary pathophysiology. Age-stratified data demonstrated that end-organ disease is progressive in JS. Most genes demonstrated a significant skew towards having variants with either residual protein function or no residual protein function. This cohort demonstrates that clinically meaningful genotype/phenotype relationships exist within most JS-related genes and can be referenced to allow for more personalized clinical care.

Novel variants identified in five Chinese families with Joubert Syndrome: a case report

BackgroundJoubert syndrome (JS) is a group of rare ciliopathies, mainly characterized by cerebellar dysplasia representing the “molar tooth sign (MTS)” on neuroimaging, hypotonia, and developmental delay. Having a complicated genotype-phenotype correlation due to its rich genetic heterogeneity, JS is usually combined with other organic defects affecting the retina, kidney, and liver. This report aimed to present new cases and novel variants of JS.Case presentationFive unrelated patients who were diagnosed with JS, with or without typical clinical characteristics, received integrated examinations, including whole-exome sequencing (WES) and Sanger sequencing. We identified nine pathogenic variants in the TCTN2, CPLANE1, INPP5E, NPHP1, and CC2D2A genes.ConclusionFour novel pathogenic mutations in the TCTN2, CPLANE1, and INPP5E genes were reported. The findings broadened the genotypic spectrum of JS and contributed to a better understanding of genotype-phenotype correlation.

Rehabilitation of a 15-month-old Child with Orofaciodigital Syndrome Type VI, Joubert Syndrome

Orofaciodigital syndrome (OFDS) type-VI, a rare subtype of Joubert syndrome, is characterized by delays in gross motor development, hypotonia, and the presence of a distinctive molar tooth sign on magnetic resonance imaging. The objective of this case report is to underscore the benefits of physiotherapy rehabilitation and delineate the clinical features associated with OFDS type VI. In this case study, we explore the details of a 15-month-old boy grappling with motor and sensory challenges related to this rare condition. The child has experienced notable improvements through play-based physiotherapy treatments, encompassing neurodevelopmental therapy, sensory integration, and adjunctive methods such as prowraps, kinesiotaping, and treadmill walking. These sessions occurred three times a week over a 10-month period. Gross motor and functional assessments, along with the Sensory Profile 2, were conducted at both the 15-month mark and when the child reached 2.1 years. The pre-GMFM score at the baseline (15th month) was 15.33, demonstrating a remarkable 57.37% improvement post-treatment at 2.1 years. Noteworthy enhancements were observed across all the dimensions of the Sensory Profile 2. This report signifies the significance of physiotherapy rehabilitation, highlighting the efficacy of a comprehensive approach involving neurodevelopmental therapy, sensory integration, and adjunct therapies.

New Insights into the Neuropsychological Profile and Intellectual Quotient Variability in Joubert Syndrome Compared to Other Congenital Cerebellar Malformations.

The neuropsychological characteristics of the cerebellar cognitive affective syndrome (CCAS) in congenital, non-progressive malformations of the cerebellum have been scarcely investigated, and even less is known for Joubert syndrome (JS), an inherited, non-progressive cerebellar ataxia characterized by the so-called molar tooth sign. The few studies on this topic reported inconsistent results about intellectual functioning and specific neuropsychological impairments. The aim of this research is to examine the neuropsychological profile of JS compared to other congenital cerebellar malformations (CM), considering individual variability of intellectual quotient (IQ) in the two groups. Fourteen patients with JS and 15 patients with CM aged 6-25 years were tested through a comprehensive, standardized neuropsychological battery. Their scores in the neuropsychological domains were inspected through descriptive analysis and compared by mean of MANOVA and ANOVA models, then replicated inserting IQ as covariate. The two groups showed a largely overlapping neuropsychological profile, consistent with CCAS. However, the JS group showed worse performance in visual-spatial memory compared to CM patients, although this difference was mitigated when considering IQ. These findings highlight a divergence between JS and other CM in visual-spatial memory, which might suggest a critical role of the cerebellum in recalling task-relevant memories and might inform rehabilitative interventions.

1035 Joubert Syndrome and severe central sleep apnea treated with noninvasive ventilation: A case report

Abstract Introduction Joubert syndrome is an autosomal recessive heterogenous ciliopathy characterized by cerebellar vermis hypoplasia resulting in ataxia, hypotonia, developmental delay, neonatal respiratory dysregulation, and abnormal eye movements. It is typically accompanied by the pathognomonic “molar tooth sign” on brain MRI. Primary central sleep apnea has been described in case reports about this condition, however given the rarity of this disease, there are very few studies conducted on these patients. Our goal is to share our treatment approaches for the sleep disturbances seen in these patients. Report of case(s) A 6-year-old female from Kuwait with a history of Joubert syndrome and global development delay presented at UCMC for evaluation of sleep issues. During the history taking, patient’s mother reported that the patient was born with acute respiratory failure shortly and required CPAP therapy in the NICU. She later developed tachypnea and cyanosis during feedings, which prompted further evaluation. A subsequent brain MRI demonstrated a molar tooth sign consistent with Joubert Syndrome. Patient required supplemental oxygenation due to nocturnal desaturations found on pulse oximetry. Due to persistent apneas and chokings during sleep, the patient underwent a repeat diagnostic polysomnogram with an electroencephalogram at our institution demonstrating severe central sleep apnea most predominant during NREM sleep. An extended montage of the EEG did not show any epileptiform discharge. This was followed by a mask de-sensitization and an inpatient PAP titration study during which BPAP therapy ST mode with a backup rate of 8 breath/minute successfully treated the patient’s primary central sleep apnea. Patient also underwent a multidisciplinary consultation with PM&R, speech therapy and ophthalmology due to her ataxia, speech delay, and need to assess for retinal dystrophy, respectively. Conclusion Sleep disordered breathing in the neonatal period is an early presentation in Joubert syndrome with central sleep apnea being the primary sleep disordered breathing. Fortunately, the clinical course of sleep disordered breathing does improve with treatment overtime, as in our case. Treatment options include conservative treatment, oxygen supplementation or PAP therapy. In our case, BPAP with ST mode was the most effective modality despite the need for mask desensitization and initial hesitation with using a PAP device. Support (if any)

TOPORS as a novel causal gene for Joubert syndrome.

Joubert syndrome (JBTS) is a Mendelian disorder of the primary cilium defined by the clinical triad of hypotonia, developmental delay, and a distinct cerebellar malformation called the molar tooth sign. JBTS is inherited in an autosomal recessive, autosomal dominant, or X-linked recessive manner. Though over 40 genes have been identified as causal for JBTS, molecular diagnosis is not made in 30%-40% of individuals who meet clinical criteria. TOPORS encodes topoisomerase I-binding arginine/serine-rich protein, and homozygosity for a TOPORS missense variant (c.29C > A; p.(Pro10Gln)) was identified in individuals with the ciliopathy oral-facial-digital syndrome in two families of Dominican descent. Here, we report an additional proband of Dominican ancestry with JBTS found by exome sequencing to be homozygous for the identical p.(Pro10Gln) TOPORS missense variant. Query of the Mount Sinai BioMe biobank, which includes 1880 individuals of Dominican ancestry, supports a high carrier frequency of the TOPORS p.(Pro10Gln) variant in individuals of Dominican descent. Our data nominates TOPORS as a novel causal gene for JBTS and suggests that TOPORS variants should be considered in the differential of ciliopathy-spectrum disease in individuals of Dominican ancestry.

Clinical and genetic analyses of Joubert syndrome in children

To study the clinical and genetic features of Joubert syndrome (JS) in children. A retrospective analysis was performed on the clinical data, genetic data, and follow-up data of 20 children who were diagnosed with JS in the Department of Children's Rehabilitation, the Third Affiliated Hospital of Zhengzhou University, from January 2017 to July 2022. Among the 20 children with JS, there were 11 boys and 9 girls. The common clinical manifestations were developmental delay (20 children, 100%), abnormal eye movement (19 children, 95%), and hypotonia (16 children, 80%), followed by abnormal respiratory rhythm in 5 children (25%) and unusual facies (including prominent forehead, low-set ears, and triangular mouth) in 3 children (15%), and no limb deformity was observed. All 20 children (100%) had the typical "molar tooth sign" and "midline cleft syndrome" on head images, and 6 children (30%) had abnormal eye examination results. Genetic testing was performed on 7 children and revealed 6 pathogenic genes, i.e., the CPLANE1, RPGRIP1L, MKS1, CC2D2A, CEP120, and AHI1 genes. For children with developmental delay, especially those with abnormal eye movement and hypotonia, it is recommended to perform a head imaging examination to determine the presence or absence of "molar tooth sign" and "midline cleft syndrome", so as to screen for JS to avoid missed diagnosis and misdiagnosis. There are many pathogenic genes for JS, and whole-exome sequencing can assist in the diagnosis of JS.

The genetic spectrum of congenital ocular motor apraxia type Cogan: an observational study, continued

BackgroundThe term congenital ocular motor apraxia (COMA), coined by Cogan in 1952, designates the incapacity to initiate voluntary eye movements performing rapid gaze shift, so called saccades. While regarded as a nosological entity by some authors, there is growing evidence that COMA designates merely a neurological symptom with etiologic heterogeneity. In 2016, we reported an observational study in a cohort of 21 patients diagnosed as having COMA. Thorough re-evaluation of the neuroimaging features of these 21 subjects revealed a previously not recognized molar tooth sign (MTS) in 11 of them, thus leading to a diagnostic reassignment as Joubert syndrome (JBTS). Specific MRI features in two further individuals indicated a Poretti–Boltshauser syndrome (PTBHS) and a tubulinopathy. In eight patients, a more precise diagnosis was not achieved. We pursued this cohort aiming at clarification of the definite genetic basis of COMA in each patient.ResultsUsing a candidate gene approach, molecular genetic panels or exome sequencing, we detected causative molecular genetic variants in 17 of 21 patients with COMA. In nine of those 11 subjects diagnosed with JBTS due to newly recognized MTS on neuroimaging, we found pathogenic mutations in five different genes known to be associated with JBTS, including KIAA0586, NPHP1, CC2D2A, MKS1, and TMEM67. In two individuals without MTS on MRI, pathogenic variants were detected in NPHP1 and KIAA0586, arriving at a diagnosis of JBTS type 4 and 23, respectively. Three patients carried heterozygous truncating variants in SUFU, representing the first description of a newly identified forme fruste of JBTS. The clinical diagnoses of PTBHS and tubulinopathy were confirmed by detection of causative variants in LAMA1 and TUBA1A, respectively. In one patient with normal MRI, biallelic pathogenic variants in ATM indicated variant ataxia telangiectasia. Exome sequencing failed to reveal causative genetic variants in the remaining four subjects, two of them with clear MTS on MRI.ConclusionsOur findings indicate marked etiologic heterogeneity in COMA with detection of causative mutations in 81% (17/21) in our cohort and nine different genes being affected, mostly genes associated with JBTS. We provide a diagnostic algorithm for COMA.