Evidence for Ritscher-Schinzel syndrome in Canadian Native Indians

Delineating the CCDC22-related Ritscher-Schinzel syndrome phenotype in the original family

Pathogenic variants in CCDC22 were initially described in 2012 in a large Australian family with intellectual disability and were subsequently noted to cause a phenotype consistent with the previously described Ritscher-Schinzel syndrome (RSS). The phenotypes of the original family were not described in detail and remains limited phenotypic data reported in medical literature. We detail the phenotypes of the original family, including newly diagnosed family members. With these eight phenotypic descriptions, more than triple the number of individuals for whom detailed clinical information is available. In addition to typical facies, common phenotypic features included intellectual disability, congenital heart disease and posterior fossa malformations, postnatal short stature, ectodermal abnormalities, and digital anomalies as previously described. Spinal curvature and genital anomalies were seen in most patients, while gastrointestinal features and disturbed sleep were also recurrently seen. We propose a possible mechanism linking the familial variant to a diagnosis of sarcoidosis in one individual. Given the clinical and genetic heterogeneity of RSS, we suggest a dyadic naming convention.

Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes

Ritscher-Schinzel syndrome (RTSCS) is a rare genetic condition characterized by peculiar craniofacial features and cerebellar and cardiovascular malformations. To date, four genes are implicated in this condition. The first two genes described were the autosomal recessive inherited gene WASHC5 associated with Ritscher-Schinzel syndrome 1 (RTSCS1), and CCDC22, an X-linked recessive gene causing Ritscher-Schinzel syndrome 2 (RTSCS2). In recent years, two other genes have been identified: VPS35L (RTSCS3) and DPYSL5 (RTSCS4). Only few patients with a molecular diagnosis of RTSCS have been reported, leaving the phenotypical spectrum and genotype-phenotype correlations ill-defined. We expand the number of genetically confirmed patients with RTSCS1 and 2; reporting three live born and three terminated pregnancies from two unrelated families. Four siblings carried compound heterozygous variants in WASHC5 while two siblings harboured a hemizygous CCDC22 variant. The most common findings in all patients were craniofacial dysmorphism, particularly macrocephaly, down slanted palpebral fissures and low set-ears. Developmental delay, intellectual disability and ataxic gait were present in all patients. One of the patients with the CCDC22 variant presented pubertas tarda. Elevation of nuchal translucency was observed in the first trimester ultrasound in three foetuses with compound heterozygous variants in WASHC5. None of the patients had epilepsy. The pre- and postnatal findings of this cohort expand the known phenotype of RTSCS1 and 2, with direct impact on postnatal outcome, management, and familial counseling.

Expansion of the CCDC22 associated Ritscher-Schinzel/3C syndrome and review of the literature: Should the minimal diagnostic criteria be revised?

The Ritscher-Schinzel syndrome (RTSCS) is a rare condition with craniofacial, cardiac and fossa posterior abnormalities. RTSCS is subdivided into Ritscher-Schinzel syndrome 1 (RTSCS1) caused by pathogenic variants in coiled-coil domain-containing protein 22 (CCDC22), and Ritscher-Schinzel syndrome 2 (RTSCS2) caused by pathogenic variants in WASH complex subunit 5 (WASHC5). CCDC22 is inherited in an X-linked recessive manner while WASHC5 is inherited in an autosomal recessive manner. Only 17 individuals with a molecular diagnosis are reported. In the past, the diagnosis of RTSCS was solely based on the clinical findings, and minimal diagnostic criteria has been proposed for the syndrome: Cardiac malformations (other than isolated patent ductus arteriosis), fossa posterior malformations, and certain dysmorphic features. However, those criteria are not present in all patients. We aim to further delineate the spectrum of CDCC22 associated RTSCS and present a novel patient with epileptic encephalopathy due to a presumed disease causing CCDC22 missense variant inherited from a healthy mother and grandmother. An affected maternal uncle had passed away at the age of 12 months and was thus unavailable for genetic testing. The proband and the maternal uncle had the typical facial dysmorphism associated with RTSCS, and they closely resembled previously published RTSCS2 patients with a molecular diagnosis. This suggests that RTSCS1 and RTSCS2 patients have a similar facial gestalt. We also review the literature on RTSCS, we explore potential differences and similarities between CCDC22 and W ASHC5 associated RTSCS and discuss the minimal diagnostic criteria.

A rare case of 3C disease: Ritscher-Schinzel syndrome presenting with recurrent talipes equinovarus

INTRODUCTION

Club foot (CF) is characterized by multiple deformities such as varus, adductus and internal rotation of the forefoot. It is well-known and a frequent congenital disorder. CF can concurrently be seen with several diseases but it can rarely manifest as a component of any other syndrome. Ritscher-Schinzel syndrome, or cranio-cerebello-cardiac syndrome, is rarely seen and has autosomal recessive inheritance. It is characterized by cranio-facial, cerebellar and cardiac abnormalities. We report a case diagnosed as Ritscher-Schinzel syndrome concurrent with persistent CF.

PRESENTATION OF CASE

A two-year-old boy with persistent CF and concurrent congenital hip dysplasia. Despite successful serial casting and subsequent achilloplasty a clinical relapse was observed in our patient. After a detailed phenotypic evaluation, genetical tests and imaging technique the patient was diagnosed 3C Ritscher-Schinzel syndrome.

DISCUSSION

A comprehensive literature review did not show any reports about concurrent hip dysplasia and clubfoot in Ritscher-Schinzel syndrome. We report that CF may be associated with rare genetical abnormalities.

CONCLUSION

With this report we would like to raise awareness about the possible association of persistent CF with this rare genetical disorder, Ritscher-Schinzel syndrome. It should be included in differential diagnosis of patients with persistent CF.

Radiographic characterization of the hands in Ritscher-Schinzel/3-C syndrome

Abstract

Ritscher-Schinzel Syndrome (RSS) is a clinically variable, autosomal recessive disorder, involving cardiac, cerebellar and craniofacial abnormalities. Numerous reports describe hand changes in RSS patients; however, a detailed characterization of the hands has not previously been performed.

Objective

The purpose of this study was to identify whether specific radiographic hand changes were characteristic of RSS and could serve as a diagnostic tool.

Materials and methods

We performed a detailed radiographic hand characterization of 8 RSS patients. The patient population consisted of 5 males and 3 females from ages one month to 26 years, 7 months. The hands were characterized using metacarpophalangeal pattern (MCPP) profiles, carpal height and bone age analyses and assessment of bone morphology.

Results

There was generalized brachydactyly with the second ray being the most severely affected. There was significant shortening of the first metacarpal and the fifth distal phalanx. The MCPP profile generated showed a consistent wavy pattern with average Z-scores ranging from -0.15 (4^th proximal phalanx) to -2.13 (1^st metacarpal) and 0.53 (4^th middle phalanx) to -1.73 (2^nd proximal phalanx) for the left and right hands, respectively. Six of eight patients showed a decreased carpal height. Bone age was within normal limits for all patients. Our study population showed consistent radiographic changes including: overtubulation of the bones (especially metacarpals 2-4), prominent tufts of the distal phalanges and a hypoplastic fifth distal phalanx.

Conclusion

The hand findings identified in this study can provide helpful diagnostic tools to clinicians when the diagnosis of RSS is being considered.

A novel mutation in KIAA0196: identification of a gene involved in Ritscher-Schinzel/3C syndrome in a First Nations cohort

BACKGROUND

Ritscher-Schinzel syndrome (RSS) is a clinically heterogeneous disorder characterised by distinctive craniofacial features in addition to cerebellar and cardiac anomalies. It has been described in different populations and is presumed to follow autosomal recessive inheritance. In an effort to identify the underlying genetic cause of RSS, affected individuals from a First Nations (FN) community in northern Manitoba, Canada, were enrolled in this study.

METHODS

Homozygosity mapping by SNP array and Sanger sequencing of the candidate genes in a 1Mb interval on chromosome 8q24.13 were performed on genomic DNA from eight FN RSS patients, eight of their parents and five unaffected individuals (control subjects) from this geographic isolate.

RESULTS

All eight patients were homozygous for a novel splice site mutation in KIAA0196. RNA analysis revealed an approximate eightfold reduction in the relative amount of a KIAA0196 transcript lacking exon 27. A 60% reduction in the amount of strumpellin protein was observed on western blot.

CONCLUSIONS

We have identified a mutation in KIAA0196 as the cause of the form of RSS characterised in our cohort. The ubiquitous expression and highly conserved nature of strumpellin, the product of KIAA0196, is consistent with the complex and multisystem nature of this disorder.

A novel multiple congenital anomaly-mental retardation syndrome with Pierre Robin sequence and cerebellar hypoplasia in two sisters

We report on the similar phenotypes and clinical course of two sisters. Both patients had an enlarged cisterna magna suggestive of cerebellar hypoplasia, agenesis/hypoplasia of the corpus callosum, Pierre Robin sequence requiring tracheostomy, camptodactyly, microphthalmia, colobomas, seizures, a distinctive facial appearance, global developmental delay, and mental retardation. We propose that the distinct pattern in these sisters constitutes a previously undescribed syndrome of likely autosomal recessive inheritance.

Segregation ratio in cranio-cerebello-cardiac syndrome

According to several authors cranio-cerebello-cardiac (3C) syndrome is an autosomal recessive disorder. This opinion was based on pedigree inspection without formal segregation analysis. Recently, the assumption of autosomal recessive inheritance was challenged by the observation of overlapping features with 6p deletions. We therefore performed segregation analysis by means of methods described by Li and Mantel, Davie and Lange on 27 pedigrees selected from literature. The results of all three methods are consistent with autosomal recessive inheritance but their broad confidence intervals leave room for other explanations as well. Reporting of 3C cases without evaluation of 6p copy number should be discouraged from now on.

Subtelomeric deletions of chromosome 6p: molecular and cytogenetic characterization of three new cases with phenotypic overlap with Ritscher-Schinzel (3C) syndrome

We have identified six children in three families with subtelomeric deletions of 6p25 and a recognizable phenotype consisting of ptosis, posterior embryotoxon, optic nerve abnormalities, mild glaucoma, Dandy-Walker malformation, hydrocephalus, atrial septal defect, patent ductus arteriosus, and mild mental retardation. There is considerable clinical overlap between these children and individuals with the Ritscher-Schinzel (or cranio-cerebello-cardiac (3C)) syndrome (OMIM #220210). Clinical features of 3C syndrome include craniofacial anomalies (macrocephaly, prominent forehead and occiput, foramina parietalia, hypertelorism, down-slanting palpebral fissures, ocular colobomas, depressed nasal bridge, narrow or cleft palate, and low-set ears), cerebellar malformations (variable manifestations of a Dandy-Walker malformation with moderate mental retardation), and cardiac defects (primarily septal defects). Since the original report, over 25 patients with 3C syndrome have been reported. Recessive inheritance has been postulated based on recurrence in siblings born to unaffected parents and parental consanguinity in two familial cases. Molecular and cytogenetic mapping of the 6p deletions in these three families with subtelomeric deletions of chromosome 6p have defined a 1.3 Mb minimally deleted critical region. To determine if 6p deletions are common in 3C syndrome, we analyzed seven unrelated individuals with 3C syndrome for deletions of this region. Three forkhead genes (FOXF1 and FOXQ1 from within the critical region, and FOXC1 proximal to this region) were evaluated as potential candidate disease genes for this disorder. No deletions or disease-causing mutations were identified.

New mental retardation syndrome associated with ocular colobomas, cleft palate, and genital, skeletal, and craniofacial abnormalities

We describe three Canadian brothers of Cree origin, with a previously undescribed pattern of malformation including distinctive craniofacial abnormalities with triangular facies, hypertelorism, low-set and posteriorly rotated ears, ocular colobomas, ptosis, brachycephaly with widely separated sutures, cleft soft palate, undescended testes, bifid scrotum and hypospadius, wide webbed neck, webbed fingers, pectus excavatum and hypersegmented sternum, and severe psychomotor retardation. The presence of normal brain imaging and physical growth distinguishes them from other syndromes with overlapping abnormalities. This is either an X-linked or autosomal recessive condition.

Dandy-walker malformation: prenatal diagnosis and outcome

Prenatal ultrasound identified Dandy-Walker malformation (DWM) in ten singleton pregnancies with concurrent central nervous system (CNS) anomalies and extra-CNS anomalies in eight cases. DWM was confirmed by postnatal magnetic resonance imaging (MRI) or pathological examination in nine cases. Karyotypes were normal in the seven infants tested. Postnatal neurological and developmental testing in the five survivors showed a spectrum of clinical outcome from minor defects to severe handicap. Postnatal investigation also disclosed additional CNS and extra-CNS findings not detected on ultrasound, as did autopsy in the other five infants. However, ultrasound diagnosis of DWM is accurate and is an indication for exhaustive screening for concurrent anomalies both within and outside the CNS and in chromosome structure and number, as the prognosis is heavily dependent on associated malformations and karyotype.

The 3C syndrome: evolution of the phenotype and growth hormone deficiency

The 3C syndrome (cranio-cerebello-cardiac dysplasia or the Ritscher-Schinzel syndrome) is a recently delineated condition involving abnormalities of the cranium (large head with prominent forehead), cerebellum (Dandy-Walker cyst and vermis hypoplasia), and cardiac (primarily septal) defects. At least 20 individuals with this condition have been reported in the past 11 years. We report on a girl with the 3C syndrome who at 13 years of age is the oldest patient reported to date. She has been followed since birth, allowing us to show the evolution of her phenotype over time. In addition, she has documented growth hormone deficiency. We suggest that growth hormone deficiency should be considered as a possible cause of the short stature often seen in this condition.

The prevalence of PAX2 mutations in patients with isolated colobomas or colobomas associated with urogenital anomalies

The PAX2 gene is mutated in patients with ocular colobomas, vesicoureteral reflux (VUR), and kidney anomalies (renal-coloboma syndrome, OMIM 120330). The three abnormalities which make up this syndrome also occur in isolation, but the causal genes are not known. PAX2 encodes a transcription factor of the paired box class of DNA binding proteins, important for the development of the urogenital tract, optic nerve and adjacent retina, inner ear, and CNS. In this paper we have investigated the prevalence of PAX2 mutations in patients with ocular colobomas, microphthalmos, or retinal anomalies, either in isolation or with associated urogenital anomalies. Using PCR-SSCP, most or all exons of PAX2 were examined in blood DNA from 99 patients who have either ocular anomalies alone or a combination of ocular and urogenital conditions. PAX2 mutations were not detected in patients with ocular colobomas, either in isolation or with associated abnormalities, except in one patient with typical renal-coloboma syndrome. We conclude that PAX2 mutations are unlikely to be common in patients with ocular colobomas in isolation or in patients with ocular colobomas and associated anomalies, except for patients with typical renal-coloboma syndrome where PAX2 is known to be the aetiological cause.

Non-progressive congenital ataxias

Congenital ataxias (CA) are rare, predominantly non-progressive syndromes characterized by marked hypotonia, developmental delay followed by the appearance of ataxia. Most children show marked speech and cognitive developmental problems. Non- progressive CA (NPCA) can be divided into pure CA without additional symptoms and syndromes with CA. Pure CA can be due to cerebellar malformations as (hereditary or non-hereditary) cerebellar hypoplasia, Dandy Walker syndrome, or occasionally supratentorial abnormalities. Ataxic syndromes are less frequent, but more distinctive. There are syndromes (e.g. Joubert syndrome) where ataxia is a cardinal feature and others where ataxia is only an occasional symptom. Acquired ataxias, due to congenital cytomegalovirus infection or perinatal problems, form a small third group. In about half of all cases with NPCA, aetiology and inheritance are still unknown. Diagnosis of NPCA is made by a typical history and careful clinical examination. Diagnosis of a more distinctive ataxic syndrome may be possible on clinical grounds. Neuroimaging with special attention to the posterior fossa will aid accurate clinical classification. Early progressive ataxias require careful differentiation from other types.

Absence of a del(22q11) in a patient with the 3C (craniocerebellocardiac) syndrome

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Screening the monoamine oxidase B gene in 100 male patients with schizophrenia: a cluster of polymorphisms in African-Americans but lack of functionally significant sequence changes

The monoamine oxidase B (MAO-B) gene was examined in 100 alleles derived from 80 Caucasian, 10 African-American, 5 Asian, and 5 Native American male patients with schizophrenia to identify sequence changes that might be associated with the disease. Approximately 235 kb of genomic sequence, primarily in coding regions, were screened by dideoxy fingerprinting, a modification of single-strand conformational polymorphism (SSCP) analysis that detects virtually 100% of sequence changes [Sarkar et al. (1992): Genomics 13:441-443; Liu and Sommer (1994): PCR Methods Appl 4:97-108]. No sequence changes of likely functional significance were identified, suggesting that mutations affecting the structure of the MAO-B protein are uncommon in the general population and are unlikely to contribute significantly to the genetic predisposition to schizophrenia. Eight polymorphisms were identified in African-Americans and Native Americans, but none were identified among Caucasians. Of the eight observed polymorphisms, a set of five transitions and one microdeletion was identified within approximately 17 kb of genomic sequence in the same 3 African-American individuals, while the remaining 7 African-Americans had a sequence identical to that in Caucasians. The presence of two such haplotypes, without intermediates, is compatible with the hypothesis that germline mutations can occur in clusters, as also suggested by other recent findings.

Ritscher-Schinzel (3C) syndrome: documentation of the phenotype

Ritscher-Schinzel syndrome or 3C (craniocerebello-cardiac) syndrome is characterized by cardiac defects, cerebellar vermis hypoplasia, and cranial defects. Nineteen cases were reported previously; however, the full spectrum of this disorder has not been determined. We have evaluated two unrelated males with this condition. Both had defects of the endocardial cushion and vermis hypoplasia with hypotonia. In addition, both had hypospadias, a previously undescribed finding of this disorders. Review of the previously reported cases and those described herein demonstrate: 1) Although varying degrees of vermis hypoplasia are accompanied by hypotonia, delayed gross motor function improves with advancing age leaving speech delay as the major neurodevelopmental handicap. 2) Two different types of cardiac anomalies occur: defects of the endocardial cushion ranging from anomalies of the mitral or tricuspid valves to complete AV canal, and/or conotruncal defects. 3) Postnatal growth deficiency was seen in most patients in whom longitudinal information was available. In our review of patients with vermis hypoplasia we ascertained a patient diagnosed as having "Joubert syndrome" who had most findings of the Ritscher-Schinzel syndrome and several other patients with "Dandy-Walker syndrome" who likely have had Ritscher-Schinzel syndrome, suggesting that Ritscher-Schinzel syndrome is more common than has been appreciated. Careful search for the subtle facial changes characteristic of this disorder as well as coloboma, cleft palate/bifid uvula, short neck, syndactyly, and hypoplasia of the nails is warranted when evaluating children with Dandy-Walker malformation with or without clinical signs of Joubert syndrome.

"Shifted" threshold may explain diversity of cardiovascular malformations in multiple congenital abnormalities syndromes: 3C (Ritscher-Schinzel) syndrome as an example

The analysis of cardiovascular malformations (CVM) in 3C (Ritscher-Schinzel) syndrome showed at least 9 types of CVM in 24 cases, including 4 cases from the Baltimore-Washington Infant Study. The proportion of different CVM forms was similar to that of the general population. The same is also true for many other syndromes of multiple congenital abnormalities (MCA), due either to aneuploidy or to Mendelian mutation. Such a wide spectrum of very different CVM in patients with the same entity has yet to be explained. According to the hypothesis proposed, the basic mutation (or chromosome imbalance) affects cellular homeostasis and leads to the "shifting" of a threshold to the left. This allows the expression of some genes silent under normal conditions. The principle of the shifted threshold is applicable to the explanation of the origin of many other defects in MCA syndromes.

A gene (RPGR) with homology to the RCC1 guanine nucleotide exchange factor is mutated in X-linked retinitis pigmentosa (RP3)

X-linked retinitis pigmentosa (xlRP) is a severe progressive retinal degeneration which affects about 1 in 25,000 of the population. The most common form of xlRP, RP3, has been localised to the interval between CYBB and OTC in Xp21.1 by linkage analysis and deletion mapping. Identification of microdeletions within this region has now led to the positional cloning of a gene, RPGR, that spans 60 kg of genomic DNA and is ubiquitously expressed. The predicted 90 kD protein contains in its N-terminal half a tandem repeat structure highly similar to RCC1 (regulator of chromosome condensation), suggesting an interaction with a small GTPase. The C-terminal half contains a domain, rich in acidic residues, and ends in a potential isoprenylation anchorage site. The two intragenic deletions, two nonsense and three missense mutations within conserved domains provide evidence that RPGR (retinitis pigmentosa GTPase regulator) is the RP3 gene.

Mechanisms of DNA expansion

Unstable transmission of repeating segments in genes is now recognized as a new class of mutations causing human disease. Genetic instability observed in disease is termed an "expansion mutation" when the mutation is an increase in the copy number of a repeated unit, commonly a di- or trinucleotide. While the expansion mutation is well characterized in disease, the mechanism by which expansion occurs is not clear. This article focuses on physical properties of expansion at repeating nucleotides that may provide clues to the mechanism. Both biochemical and genetic data indicate that DNA structure is part of the mechanism and the underlying cause for expansion.