Hypothalamic hamartoma in oral-facial-digital syndrome type VI (Váradi syndrome)

Clinical and molecular heterogeneity of syndromic hypothalamic hamartoma

Two children are presented who have a distinct syndrome of multiple buccolingual frenula, a stiff and short fifth finger with small nails, a hypothalamic hamartoma, mild to moderate neurological impairment, and mild endocrinological symptoms. No variant assessed to be pathogenic or likely pathogenic was detected in the GLI3 gene in either child. This syndrome appears to be distinct from the inherited Pallister-Hall syndrome associated with GLI3 variants, which is characterized by hypothalamic hamartoma, mesoaxial polydactyly, and other anomalies. In the individuals described here, manifestations outside of the central nervous system were milder and the mesoaxial polydactyly, which is common in individuals with Pallister-Hall syndrome, was absent. Instead, these children had multiple buccolingual frenula together with the unusual appearance of the fifth digit. It remains unclear whether these two individuals represent a separate nosologic entity or if they represent a milder manifestation of one of the more severe syndromes associated with a hypothalamic hamartoma.

Novel mutations in the ciliopathy-associated gene CPLANE1 (C5orf42) cause OFD syndrome type VI rather than Joubert syndrome

Mutations in CPLANE1 (previously known as C5orf42) cause Oral-Facial-Digital Syndrome type VI (OFD6) as well as milder Joubert syndrome (JS) phenotypes. Seven new cases from five unrelated families diagnosed with pure OFD6 were systematically examined. Based on the clinical manifestations of these patients and those described in the literature, we revised the diagnostic features of OFD6 and include the seven most common characteristics: 1) molar tooth sign, 2) tongue hamartoma and/or lobulated tongue, 3) additional frenula, 4) mesoaxial polydactyly of hands, 5) preaxial polydactyly of feet, 6) syndactyly and/or bifid toe, and 7) hypothalamic hamartoma. By whole or targeted exome sequencing, we identified seven novel germline recessive mutations in CPLANE1, including missense, nonsense, frameshift and canonical splice site variants, all causing OFD6 in these patients. Since CPLANE1 is also mutated in JS patients, we examined whether a genotype-phenotype correlation could be established. We gathered and compared 46 biallelic CPLANE1 mutations reported in 32 JS and 26 OFD6 patients. Since no clear correlation between paired genotypes and clinical outcomes could be determined, we concluded that patient's genetic background and gene modifiers may modify the penetrance and expressivity of CPLANE1 causal alleles. To conclude, our study provides a comprehensive view of the phenotypic range, the genetic basis and genotype-phenotype association in OFD6 and JS. The updated phenotype scoring system together with the identification of new CPLANE1 mutations will help clinicians and geneticists reach a more accurate diagnosis for JS-related disorders.

Exome sequencing identifies a homozygous C5orf42 variant in a Turkish kindred with oral-facial-digital syndrome type VI

Oral-facial-digital syndrome type VI (OFDVI) is a rare ciliopathy in the spectrum of Joubert syndrome (JS) and distinguished from other oral-facial-digital syndromes by metacarpal abnormalities with central polydactyly and by a molar tooth sign on cranial MRI. Additional characteristic features include short stature, micrognathia, posteriorly rotated low-set ears, hypertelorism, epicanthal folds, broad nasal tip, tongue hamartoma, upper lip notch, intraoral frenula, cleft lip/palate, and renal anomalies. Recently, novel mutations in C5orf42 were identified in 9 out of 11 OFDVI families. In a subsequent study C5orf42 was found to be mutated in only 2 out of 17 OFDVI probands while 28 patients with a pure JS phenotype also had pathogenic mutations of C5orf42. We report on two affected cousins diagnosed with OFDVI who were born from first degree cousin marriages. Whole exome sequencing (WES) identified a homozygous predicted damaging missense mutation (c.4034A > G; p.Gln1345Arg) in the C5orf42 gene. Our data contribute to the evidence that C5orf42 is one of the causative genes for OFDVI.

C5orf42 is the major gene responsible for OFD syndrome type VI

Oral-facial-digital syndrome type VI (OFD VI) is a recessive ciliopathy defined by two diagnostic criteria: molar tooth sign (MTS) and one or more of the following: (1) tongue hamartoma (s) and/or additional frenula and/or upper lip notch; (2) mesoaxial polydactyly of one or more hands or feet; (3) hypothalamic hamartoma. Because of the MTS, OFD VI belongs to the "Joubert syndrome related disorders". Its genetic aetiology remains largely unknown although mutations in the TMEM216 gene, responsible for Joubert (JBS2) and Meckel-Gruber (MKS2) syndromes, have been reported in two OFD VI patients. To explore the molecular cause(s) of OFD VI syndrome, we used an exome sequencing strategy in six unrelated families followed by Sanger sequencing. We identified a total of 14 novel mutations in the C5orf42 gene in 9/11 families with positive OFD VI diagnostic criteria including a severe fetal case with microphthalmia, cerebellar hypoplasia, corpus callosum agenesis, polydactyly and skeletal dysplasia. C5orf42 mutations have already been reported in Joubert syndrome confirming that OFD VI and JBS are allelic disorders, thus enhancing our knowledge of the complex, highly heterogeneous nature of ciliopathies.

Delineation and diagnostic criteria of Oral-Facial-Digital Syndrome type VI

Oral-Facial-Digital Syndrome type VI (OFD VI) represents a rare phenotypic subtype of Joubert syndrome and related disorders (JSRD). In the original report polydactyly, oral findings, intellectual disability, and absence of the cerebellar vermis at post-mortem characterized the syndrome. Subsequently, the molar tooth sign (MTS) has been found in patients with OFD VI, prompting the inclusion of OFD VI in JSRD. We studied the clinical, neurodevelopmental, neuroimaging, and genetic findings in a cohort of 16 patients with OFD VI. We derived the following inclusion criteria from the literature: 1) MTS and one oral finding and polydactyly, or 2) MTS and more than one typical oral finding. The OFD VI neuroimaging pattern was found to be more severe than in other JSRD subgroups and includes severe hypoplasia of the cerebellar vermis, hypoplastic and dysplastic cerebellar hemispheres, marked enlargement of the posterior fossa, increased retrocerebellar collection of cerebrospinal fluid, abnormal brainstem, and frequently supratentorial abnormalities that occasionally include characteristic hypothalamic hamartomas. Additionally, two new JSRD neuroimaging findings (ascending superior cerebellar peduncles and fused thalami) have been identified. Tongue hamartomas, additional frenula, upper lip notch, and mesoaxial polydactyly are specific findings in OFD VI, while cleft lip/palate and other types of polydactyly of hands and feet are not specific. Involvement of other organs may include ocular findings, particularly colobomas. The majority of the patients have absent motor development and profound cognitive impairment. In OFD VI, normal cognitive functions are possible, but exceptional. Sequencing of known JSRD genes in most patients failed to detect pathogenetic mutations, therefore the genetic basis of OFD VI remains unknown. Compared with other JSRD subgroups, the neurological findings and impairment of motor development and cognitive functions in OFD VI are significantly worse, suggesting a correlation with the more severe neuroimaging findings. Based on the literature and this study we suggest as diagnostic criteria for OFD VI: MTS and one or more of the following: 1) tongue hamartoma(s) and/or additional frenula and/or upper lip notch; 2) mesoaxial polydactyly of one or more hands or feet; 3) hypothalamic hamartoma.

Joubert syndrome and related disorders: spectrum of neuroimaging findings in 75 patients

VH and MTS are the neuroimaging hallmarks of JSRD. We aimed to look at the full spectrum of neuroimaging findings in JSRD and reviewed the MR imaging of 75 patients with JSRD, including 13 siblings and 4 patients with OFD VI. All patients had VH and enlargement of the fourth ventricle. The degree of VH and the form of the MTS were variable. In most patients, the cerebellar hemispheres were normal and the PF was enlarged. Brain stem morphology was abnormal in 30% of the patients. Supratentorial findings included hippocampal malrotation, callosal dysgenesis, migration disorders, cephaloceles, and ventriculomegaly. All patients with OFD VI had a similar pattern, including HH in 2 patients. No neuroimaging-genotype correlation could be found. The wide neuroimaging spectrum in our patients supports the heterogeneity of JSRD. Neuroimaging differences in siblings represent intrafamilial heterogeneity. Due to the absence of a correlation with genotype, neuroimaging findings are of limited value in classifying patients with JSRD.

Molecular analysis expands the spectrum of phenotypes associated with GLI3 mutations

A range of phenotypes including Greig cephalopolysyndactyly and Pallister-Hall syndromes (GCPS, PHS) are caused by pathogenic mutation of the GLI3 gene. To characterize the clinical variability of GLI3 mutations, we present a subset of a cohort of 174 probands referred for GLI3 analysis. Eighty-one probands with typical GCPS or PHS were previously reported, and we report the remaining 93 probands here. This includes 19 probands (12 mutations) who fulfilled clinical criteria for GCPS or PHS, 48 probands (16 mutations) with features of GCPS or PHS but who did not meet the clinical criteria (sub-GCPS and sub-PHS), 21 probands (6 mutations) with features of PHS or GCPS and oral-facial-digital syndrome, and 5 probands (1 mutation) with nonsyndromic polydactyly. These data support previously identified genotype-phenotype correlations and demonstrate a more variable degree of severity than previously recognized. The finding of GLI3 mutations in patients with features of oral-facial-digital syndrome supports the observation that GLI3 interacts with cilia. We conclude that the phenotypic spectrum of GLI3 mutations is broader than that encompassed by the clinical diagnostic criteria, but the genotype-phenotype correlation persists. Individuals with features of either GCPS or PHS should be screened for mutations in GLI3 even if they do not fulfill clinical criteria.

Joubert Syndrome and related disorders

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.

Prenatal and neonatal MR imaging findings in oral-facial-digital syndrome type VI

We report prenatal and neonatal neuroimaging findings in a case of oral-facial-digital syndrome type VI (OFDS VI). Prenatal MR imaging at 29 weeks' gestation showed hypoplastic cerebellar vermis and hemispheres, the molar tooth sign, and a hypothalamic hamartoma. Neonatal MR imaging confirmed these findings. The neonate developed breathing abnormalities and exhibited frontal bossing, multiple bucco-alveolar frenula, and postaxial hexadactyly of both hands. If the molar tooth sign and a hypothalamic hamartoma are present, prenatal diagnosis of OFDS VI is possible.

Oral-facial-digital syndromes: review and diagnostic guidelines

The oral-facial-digital syndromes (OFDS) result from the pleiotropic effect of a morphogenetic impairment affecting almost invariably the mouth, face and digits. Other organ systems can be involved, defining specific types of OFDS. To date, 13 types have been distinguished based on characteristic clinical manifestations. An updated list of these types is provided and recent molecular data are discussed.

Orofaciodigital syndrome with cerebral dysgenesis

Orofaciodigital syndromes (OFD) are a group of diseases classified according to the phenotype and the mode of inheritance. We report on a fetus presenting with some features of the OFDs but with additional global cerebral dysgenesis. Ultrasonography at 19 weeks of pregnancy disclosed hypoplasia of the cerebral hemispheres with a large intrahemispheric cyst, as well as dysmorphic facial features and brachy-syndactyly IV-V. Fetal brain MRI confirmed these features and disclosed additional morphological anomalies: Agenesis of the vermis, complete agenesis of the corpus callosum, pachygyria of the left hemisphere. Pathological examination showed a disproportionate fetus with large head and short limbs. Dysmorphic features included hypertelorism, broad nasal root, long philtrum, severe micrognathia, microstomia, cleft palate, and lobulated tongue. Radiographs showed distal malformations of the four limbs. Neuropathological examination showed a severe disturbance of the architecture of both hemispheres, more severe on the right side, with four cystic structures located between the hemispheres. Olfactory stalks, mammillary bodies, and midline structures were absent. Cerebellum and brainstem were hypoplastic. On the right hemisphere as on most part of the left one, microscopic findings displayed a complete disruption of the developing mantle with disturbance of the neuronal migration. The present fetus fulfilled the diagnosis of OFD syndrome: Dysmorphic features, cleft palate and lobulate tongue and polysyndactylies of the feet and hands. The cerebral involvement would make it closer to OFD type VI, but brain malformations were far more severe in the present case, with complex and generalized cortical dysgenesis, evoking a disturbance occurring at a very early stage of the embryogenesis.

Molar tooth sign of the midbrain-hindbrain junction: occurrence in multiple distinct syndromes

The Molar Tooth Sign (MTS) is defined by an abnormally deep interpeduncular fossa; elongated, thick, and mal-oriented superior cerebellar peduncles; and absent or hypoplastic cerebellar vermis that together give the appearance of a "molar tooth" on axial brain MRI through the junction of the midbrain and hindbrain (isthmus region). It was first described in Joubert syndrome (JS) where it is present in the vast majority of patients with this diagnosis. We previously showed that the MTS is a component of several other syndromes, including Dekaban-Arima (DAS), Senior-Löken, and COACH (cerebellar vermis hypoplasia (CVH), oligophrenia, ataxia, coloboma, and hepatic fibrosis). Here we present evidence that the MTS is seen together with polymicrogyria, Váradi-Papp syndrome (Orofaciodigital VI (OFD VI)), and a new syndrome with encephalocele and cortical renal cysts. We also present a new patient with COACH syndrome plus the MTS. We propose that the MTS is found in multiple distinct clinical syndromes that may share common developmental mechanisms. Proper classification of patients with these variants of the MTS will be essential for localization and identification of mutant genes.

Penile agenesis and clavicular anomaly in a child with an oral facial digital syndrome

We report a male patient with the clinical characteristics of an OFDS (oral facial digital syndrome). He also has penile agenesis, clavicular flattening and cerebellar anomalies. This patient was classified as a severe form of OFD type II-Mohr syndrome but the possibility of this being OFDS VI-Varadi syndrome or a new form of OFDS cannot completely be excluded.

Hypothalamic hamartoma as a cause of precocious puberty in neurofibromatosis type 1: patient report

Precocious puberty resulting from hypothalamic hamartoma is well known. Neurofibromatosis type 1 can also present with precocious puberty. However, hypothalamic hamartoma as the cause of precocious puberty in patients with neurofibromatosis type 1 has never been described in the literature. This rare occurrence of these two together in a patient with precocious puberty is reported.

Neuropathologic findings in a case of OFDS type VI (Váradi syndrome)

Oral-facial-digital syndrome type VI (OFDS VI) or Váradi syndrome is a rare autosomal-recessive disorder distinguished from other oral-facial-digital syndromes by metacarpal abnormalities with central polydactyly and by cerebellar abnormalities. Histopathologic characterization of the cerebellar abnormalities has not been described previously. We describe the neuropathologic findings in a stillborn, 21-week estimated gestational age (EGA) male fetus diagnosed antenatally with signs of OFDS VI. Autopsy findings included: facial abnormalities, postaxial central polydactyly of the right hand, bilateral bifid toes, and absence of cerebellar vermis with hypoplasia of the hemispheric cortex. Microscopic analysis of the cerebellum demonstrated absence of the subpial granular cell layer and disruption or dysgenesis of the glial architecture. These histopathologic findings suggest that a primary neuronal or glial cell defect, rather than an associated Dandy-Walker malformation, may account for the cerebellar abnormalities in this form of oral-facial-digital syndrome.

Autosomal dominant inheritance of hypothalamic hamartoma associated with polysyndactyly: heterogeneity or variable expressivity?

We report on a two-generation family exhibiting dominant inheritance of complex polysyndactyly associated with hypothalamic hamartoma. These individuals have some manifestations of Pallister-Hall syndrome (PHS), but their phenotype is milder. The proposita is a 16-year-old girl with polysyndactyly of the hands and feet, short stature, and a large hypothalamic hamartoma. Her brother and father also have polysyndactyly and a hypothalamic mass on MRI scan. All three have normal appearance and intelligence, with normal pituitary function. Several other paternal relatives have polysyndactyly as well. We propose that this family may represent a clinically and perhaps genetically distinct entity from PHS, based on normal survival, normal intelligence, lack of endocrine dysfunction or facial anomalies, and few other structural malformations. Linkage analysis is in progress to determine whether this represents a benign form of PHS or a genetically separate condition. The phenotypic differences between these cases and classic PHS have important prognostic and recurrence risk implications.

Pallister-Hall syndrome

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