Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: Report of four new cases and review

Clinical and molecular characteristics of 26 fetuses with lethal multiple congenital contractures

Multiple congenital contractures (MCC) due to fetal akinesia manifest across a broad spectrum of diseases, ranging from mild distal arthrogryposis to lethal fetal akinesia deformation sequence. We hereby present a series of 26 fetuses displaying severe MCC phenotypes from 18 families and describe detailed prenatal ultrasound findings, postmortem clinical evaluations, and genetic investigations. Most common prenatal findings were abnormal facial profile (65%), central nervous system abnormalities (62%), polyhydramnios (50%), increased nuchal translucency (50%), and fetal hydrops (35%). Postmortem examinations unveiled additional anomalies including facial dysmorphisms, dysplastic skeletal changes, ichthyosis, multiple pterygia, and myopathy, allowing preliminary diagnosis of particular Mendelian disorders in multiple patients. Evaluation of the parents revealed maternal grip myotonia in one family. By exome sequencing and targeted testing, we identified causative variants in ACTC1, CHST14, COG6, DMPK, DOK7, HSPG2, KLHL7, KLHL40, KIAA1109, NEB, PSAT1, RAPSN, USP14, and WASHC5 in 15 families, and one patient with a plausible diagnosis associated with biallelic NEB variants. Three patients received a dual diagnosis. Pathogenic alterations in newly discovered genes or in previously known genes recently linked to new MCC phenotypes were observed in 44% of the cohort. Our results provide new insights into the clinical and molecular landscape of lethal MCC phenotypes.

Helper T cell immunity in humans with inherited CD4 deficiency

CD4+ T cells are vital for host defense and immune regulation. However, the fundamental role of CD4 itself remains enigmatic. We report seven patients aged 5-61 years from five families of four ancestries with autosomal recessive CD4 deficiency and a range of infections, including recalcitrant warts and Whipple's disease. All patients are homozygous for rare deleterious CD4 variants impacting expression of the canonical CD4 isoform. A shorter expressed isoform that interacts with LCK, but not HLA class II, is affected by only one variant. All patients lack CD4+ T cells and have increased numbers of TCRαβ+CD4-CD8- T cells, which phenotypically and transcriptionally resemble conventional Th cells. Finally, patient CD4-CD8- αβ T cells exhibit intact responses to HLA class II-restricted antigens and promote B cell differentiation in vitro. Thus, compensatory development of Th cells enables patients with inherited CD4 deficiency to acquire effective cellular and humoral immunity against an unexpectedly large range of pathogens. Nevertheless, CD4 is indispensable for protective immunity against at least human papillomaviruses and Trophyrema whipplei.

Surveillance of multiple congenital anomalies; searching for new associations

Many human teratogens are associated with a spectrum of congenital anomalies rather than a single defect, and therefore the identification of congenital anomalies occurring together more frequently than expected may improve the detection of teratogens. Thirty-two EUROCAT congenital anomaly registries covering 6,599,765 births provided 123,566 cases with one or more major congenital anomalies (excluding chromosomal and genetic syndromes) for the birth years 2008-2016. The EUROCAT multiple congenital anomaly algorithm identified 8804 cases with two or more major congenital anomalies in different organ systems, that were not recognized as part of a syndrome or sequence. For each pair of anomalies, the odds of a case having both anomalies relative to having only one anomaly was calculated and the p value was estimated using a two-sided Fisher's exact test. The Benjamini-Hochberg procedure adjusted p values to control the false discovery rate and pairs of anomalies with adjusted p values < 0.05 were identified. A total of 1386 combinations of two anomalies were analyzed. Out of the 31 statistically significant positive associations identified, 20 were found to be known associations or sequences already described in the literature and 11 were considered "potential new associations" by the EUROCAT Coding and Classification Committee. After a review of the literature and a detailed examination of the individual cases with the anomaly pairs, six pairs remained classified as new associations. In summary, systematically searching for congenital anomalies occurring together more frequently than expected using the EUROCAT database is worthwhile and has identified six new associations that merit further investigation.

Understanding the Genetic and Non-Genetic Interconnections in the Aetiology of Syndromic Congenital Heart Disease: An Updated Review: Part 2

PURPOSE OF REVIEW

Approximately 30% of syndromic cases diagnosed with CHD, which lure us to further investigate the molecular and clinical challenges behind syndromic CHD (sCHD). The aetiology of sCHD in a majority of cases remains enigmatic due to involvement of multiple factors, namely genetic, epigenetic and environmental modifiable risk factors for the development of the disease. Here, we aim to update the role of genetic contributors including chromosomal abnormalities, copy number variations (CNVs) and single gene mutations in cardiac specific genes, maternal lifestyle conditions, environmental exposures and epigenetic modifiers in causing CHD in different genetic syndromes.

RECENT FINDINGS

The exact aetiology of sCHD is still unknown. With the advancement of next-generation technologies including WGS, WES, transcriptome, proteome and methylome study, numerous novel genes and pathways have been identified. Moreover, our recent knowledge regarding epigenetic and environmental regulation during cardiogenesis is still evolving and may solve some of the mystery behind complex sCHD. Here, we focus to understand how the complex combination of genetic, environmental and epigenetic factors interact to interfere with developmental pathways, culminating into cardiac and extracardiac defects in sCHD.

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.

N471D WASH complex subunit strumpellin knock-in mice display mild motor and cardiac abnormalities and BPTF and KLHL11 dysregulation in brain tissue

AIMS

We investigated N471D WASH complex subunit strumpellin (Washc5) knock-in and Washc5 knock-out mice as models for hereditary spastic paraplegia type 8 (SPG8).

METHODS

We generated heterozygous and homozygous N471D Washc5 knock-in mice and subjected them to a comprehensive clinical, morphological and laboratory parameter screen, and gait analyses. Brain tissue was used for proteomic analysis. Furthermore, we generated heterozygous Washc5 knock-out mice. WASH complex subunit strumpellin expression was determined by qPCR and immunoblotting.

RESULTS

Homozygous N471D Washc5 knock-in mice showed mild dilated cardiomyopathy, decreased acoustic startle reactivity, thinner eye lenses, increased alkaline phosphatase and potassium levels and increased white blood cell counts. Gait analyses revealed multiple aberrations indicative of locomotor instability. Similarly, the clinical chemistry, haematology and gait parameters of heterozygous mice also deviated from the values expected for healthy animals, albeit to a lesser extent. Proteomic analysis of brain tissue depicted consistent upregulation of BPTF and downregulation of KLHL11 in heterozygous and homozygous knock-in mice. WASHC5-related protein interaction partners and complexes showed no change in abundancies. Heterozygous Washc5 knock-out mice showing normal WASHC5 levels could not be bred to homozygosity.

CONCLUSIONS

While biallelic ablation of Washc5 was prenatally lethal, expression of N471D mutated WASHC5 led to several mild clinical and laboratory parameter abnormalities, but not to a typical SPG8 phenotype. The consistent upregulation of BPTF and downregulation of KLHL11 suggest mechanistic links between the expression of N471D mutated WASHC5 and the roles of both proteins in neurodegeneration and protein quality control, respectively.

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.

Phenotype-genotype comorbidity analysis of patients with rare disorders provides insight into their pathological and molecular bases

Genetic and molecular analysis of rare disease is made difficult by the small numbers of affected patients. Phenotypic comorbidity analysis can help rectify this by combining information from individuals with similar phenotypes and looking for overlap in terms of shared genes and underlying functional systems. However, few studies have combined comorbidity analysis with genomic data. We present a computational approach that connects patient phenotypes based on phenotypic co-occurence and uses genomic information related to the patient mutations to assign genes to the phenotypes, which are used to detect enriched functional systems. These phenotypes are clustered using network analysis to obtain functionally coherent phenotype clusters. We applied the approach to the DECIPHER database, containing phenotypic and genomic information for thousands of patients with heterogeneous rare disorders and copy number variants. Validity was demonstrated through overlap with known diseases, co-mention within the biomedical literature, semantic similarity measures, and patient cluster membership. These connected pairs formed multiple phenotype clusters, showing functional coherence, and mapped to genes and systems involved in similar pathological processes. Examples include claudin genes from the 22q11 genomic region associated with a cluster of phenotypes related to DiGeorge syndrome and genes related to the GO term anterior/posterior pattern specification associated with abnormal development. The clusters generated can help with the diagnosis of rare diseases, by suggesting additional phenotypes for a given patient and potential underlying functional systems. Other tools to find causal genes based on phenotype were also investigated. The approach has been implemented as a workflow, named PhenCo, which can be adapted to any set of patients for which phenomic and genomic data is available. Full details of the analysis, including the clusters formed, their constituent functional systems and underlying genes are given. Code to implement the workflow is available from GitHub.

Although rare diseases each affect a small number of people, taken together they affect millions. Better diagnosis and understanding of the underlying mechanisms are needed. By combining phenotypic data for many rare disease patients, we can build clusters of comorbid phenotypes that tend to co-occur together. By using genomic information, we can supplement these clusters and look for related genes and functional systems, such as pathways and molecular mechanisms. We applied such an approach to thousands of rare disease patients from the DECIPHER resources. We were able to detect hundreds of pairs of comorbid phenotypes, and use them to build tens of phenotype clusters. By mapping genes to these phenotypes, based on data from the same patients, we were able to detect related genes and functional systems, such as genes mapping to the 22q11 genomic region underlying a cluster of phenotypes related to DiGeorge syndrome. To ensure that these clusters made sensible predictions, results were validated using literature co-mention, overlap with known disease and semantic similarity measures. These comorbidity patterns, along with their underlying molecular systems, can give important insights into disease mechanisms, moreover they can be used to direct differential-diagnosis of rare disease patients.

Genetics of syndromic ocular coloboma: CHARGE and COACH syndromes

Optic fissure closure defects result in uveal coloboma, a potentially blinding condition affecting between 0.5 and 2.6 per 10,000 births that may cause up to 10% of childhood blindness. Uveal coloboma is on a phenotypic continuum with microphthalmia (small eye) and anophthalmia (primordial/no ocular tissue), the so-called MAC spectrum. This review gives a brief overview of the developmental biology behind coloboma and its clinical presentation/spectrum. Special attention will be given to two prominent, syndromic forms of coloboma, namely, CHARGE (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, and Ear anomalies/deafness) and COACH (Cerebellar vermis hypoplasia, Oligophrenia, Ataxia, Coloboma, and Hepatic fibrosis) syndromes. Approaches employed to identify genes involved in optic fissure closure in animal models and recent advances in live imaging of zebrafish eye development are also discussed.

Biallelic VPS35L pathogenic variants cause 3C/Ritscher-Schinzel-like syndrome through dysfunction of retriever complex

BACKGROUND

3C/Ritscher-Schinzel syndrome is characterised by congenital cranio-cerebello-cardiac dysplasia, where CCDC22 and WASHC5 are accepted as the causative genes. In combination with the retromer or retriever complex, these genes play a role in endosomal membrane protein recycling. We aimed to identify the gene abnormality responsible for the pathogenicity in siblings with a 3C/Ritscher-Schinzel-like syndrome, displaying cranio-cerebello-cardiac dysplasia, coloboma, microphthalmia, chondrodysplasia punctata and complicated skeletal malformation.

METHODS

Exome sequencing was performed to identify pathogenic variants. Cellular biological analyses and generation of knockout mice were carried out to elucidate the gene function and pathophysiological significance of the identified variants.

RESULTS

We identified compound heterozygous pathogenic variants (c.1097dup; p.Cys366Trpfs*28 and c.2755G>A; p.Ala919Thr) in the VPS35L gene, which encodes a core protein of the retriever complex. The identified missense variant lacked the ability to form the retriever complex, and the frameshift variant induced non-sense-mediated mRNA decay, thereby confirming biallelic loss of function of VPS35L. In addition, VPS35L knockout cells showed decreased autophagic function in nutrient-rich and starvation conditions, as well as following treatment with Torin 1. We also generated Vps35l^-/- mice and demonstrated that they were embryonic lethal at an early stage, between E7.5 and E10.5.

CONCLUSIONS

Our results suggest that biallelic loss-of-function variants in VPS35L underlies 3C/Ritscher-Schinzel-like syndrome. Furthermore, VPS35L is necessary for autophagic function and essential for early embryonic development. The data presented here provide a new insight into the critical role of the retriever complex in fetal development.

Neuroimaging Findings in Pediatric Genetic Skeletal Disorders: A Review

Genetic skeletal disorders (GSDs) are a heterogeneous group characterized by an intrinsic abnormality in growth and (re-)modeling of cartilage and bone. A large subgroup of GSDs has additional involvement of other structures/organs beside the skeleton, such as the central nervous system (CNS). CNS abnormalities have an important role in long-term prognosis of children with GSDs and should consequently not be missed. Sensitive and specific identification of CNS lesions while evaluating a child with a GSD requires a detailed knowledge of the possible associated CNS abnormalities. Here, we provide a pattern-recognition approach for neuroimaging findings in GSDs guided by the obvious skeletal manifestations of GSD. In particular, we summarize which CNS findings should be ruled out with each GSD. The diseases (n = 180) are classified based on the skeletal involvement (1. abnormal metaphysis or epiphysis, 2. abnormal size/number of bones, 3. abnormal shape of bones and joints, and 4. abnormal dynamic or structural changes). For each disease, skeletal involvement was defined in accordance with Online Mendelian Inheritance in Man. Morphological CNS involvement has been described based on extensive literature search. Selected examples will be shown based on prevalence of the diseases and significance of the CNS involvement. CNS involvement is common in GSDs. A wide spectrum of morphological abnormalities is associated with GSDs. Early diagnosis of CNS involvement is important in the management of children with GSDs. This pattern-recognition approach aims to assist and guide physicians in the diagnostic work-up of CNS involvement in children with GSDs and their management.

Missense variant in CCDC22 causes X-linked recessive intellectual disability with features of Ritscher-Schinzel/3C syndrome

Ritscher-Schinzel syndrome (RSS)/3C (cranio-cerebro-cardiac) syndrome (OMIM#220210) is a rare and clinically heterogeneous developmental disorder characterized by intellectual disability, cerebellar brain malformations, congenital heart defects, and craniofacial abnormalities. A recent study of a Canadian cohort identified homozygous sequence variants in the KIAA0196 gene, which encodes the WASH complex subunit strumpellin, as a cause for a form of RSS/3C syndrome. We have searched for genetic causes of a phenotype similar to RSS/3C syndrome in an Austrian family with two affected sons. To search for disease-causing variants, whole-exome sequencing (WES) was performed on samples from two affected male children and their parents. Before WES, CGH array comparative genomic hybridization was applied. Validation of WES and segregation studies was done using routine Sanger sequencing. Exome sequencing detected a missense variant (c.1670A>G; p.(Tyr557Cys)) in exon 15 of the CCDC22 gene, which maps to chromosome Xp11.23. Western blots of immortalized lymphoblastoid cell lines (LCLs) from the affected individual showed decreased expression of CCDC22 and an increased expression of WASH1 but a normal expression of strumpellin and FAM21 in the patients cells. We identified a variant in CCDC22 gene as the cause of an X-linked phenotype similar to RSS/3C syndrome in the family described here. A hypomorphic variant in CCDC22 was previously reported in association with a familial case of syndromic X-linked intellectual disability, which shows phenotypic overlap with RSS/3C syndrome. Thus, different inactivating variants affecting CCDC22 are associated with a phenotype similar to RSS/3C syndrome.

Molecular Karyotyping of a Dysmorphic Girl from Saudi Arabia with CYP1B1-negative Primary Congenital Glaucoma

PURPOSE

To report the results of molecular karyotyping for a dysmorphic girl with CYP1B1-negative primary congenital glaucoma from Saudi Arabia, where CYPB1 mutations account for over 90% of cases of primary congenital glaucoma and the remaining cases are idiopathic.

METHODS

CYP1B1 sequencing in the affected child; high-resolution array comparative genomic hybridization (array CGH) of the affected child and both unaffected parents (Affymetrix Cytogenetics Whole-Genome 2.7M array; Affymetrix Inc., Santa Clara, CA, USA).

RESULTS

The girl did not harbor CYP1B1 mutation by Sanger sequencing. Array CGH revealed 2 de novo 7p heterozygous duplications (7p21 - 7p14, encompassing 223 genes, and 7p14-7p11.2, encompassing 225 genes) and a 4p homozygous microdeletion (4p14) encompassing one gene only, DTHD1.

CONCLUSIONS

The fact that this dysmorphic girl is Saudi Arabian and has CYP1B1-negative primary congenital glaucoma suggests that her glaucoma phenotype is related to her de novo copy number variation. Loss or gain of one or more of the genes encompassed in the identified chromosomal areas may be associated with primary congenital glaucoma and/or other observed phenotypic features.

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.

Diffusion tensor imaging and fiber tractography in brain malformations

Diffusion tensor imaging (DTI) is an advanced MR technique that provides qualitative and quantitative information about the micro-architecture of white matter. DTI and its post-processing tool fiber tractography (FT) have been increasingly used in the last decade to investigate the microstructural neuroarchitecture of brain malformations. This article aims to review the use of DTI and FT in the evaluation of a variety of common, well-described brain malformations, in particular by pointing out the additional information that DTI and FT renders compared with conventional MR sequences. In addition, the relevant existing literature is summarized.

Dandy-Walker's variant and tetralogy of Fallot with atrial septal defect and patent ductus arteriosus and primary hypothyroidy--a new association

An 11-month-old girl who has Dandy-Walker's variant (DWV) associated with tetralogy of Fallot (TOF), atrial septal defect (ASD), patent ductus arteriosus (PDA), and primary hypothyroidy is presented. There has been no report describing a case of DWV associated with TOF, ASD and PDA and primary hypothyroidy. The first case of Dandy-Walker malformation associated with TOF was reported by Kohyama et al in 1988, since then, a few cases were reported in the literature. Our patient is the first reported case.

The 6p subtelomere deletion syndrome

Submicroscopic deletion of the 6p25 subtelomere has recently been recognized as a clinically identifiable syndrome. To date, more than 30 cases have been described with variable cytogenetically visible 6p deletions. Terminal 6p deletions result in a clinically distinguishable phenotype. The focus of this review is the phenotype associated with isolated terminal deletions of 6p25, and specifically isolated submiscroscopic subtelomere deletions. A distinct phenotype has emerged consisting of developmental delay/mental retardation, language impairment, hearing loss, and ophthalmologic, cardiac, and craniofacial abnormalities. These features demonstrate considerable clinical overlap with the Ritscher-Schinzel (or cranio-cerebello-cardiac (3C)) syndrome (OMIM #220210). Isolated submiscroscopic 6p25 subtelomere terminal deletion has been reported in 11 individuals, two of whom are siblings. Cytogentic and molecular mapping of the 6p25 deletion boundary has been reported in 8 of these 10 unrelated individuals with isolated submiscroscopic subtelomere deletion. This analysis has revealed substantial phenotypic overlap between individuals with submicroscopic terminal 6p deletions and those with large, cytogenetically visible deletions of the region suggesting that the critical genes contributing to the main clinical and developmental features lie in the terminal region of 6p25.

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.

Uveal coloboma: clinical and basic science update

PURPOSE OF REVIEW

To integrate knowledge on the embryologic and molecular basis of optic fissure closure with clinical observations in patients with uveal coloboma.

RECENT FINDINGS

Closure of the optic fissure has been well characterized and many genetic alterations have been associated with coloboma; however, molecular mechanisms leading to coloboma remain largely unknown. In the past decade, we have gained better understanding of genes critical to eye development; however, mutations in these genes have been found in few individuals with coloboma. CHD7 mutations have been identified in patients with CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth, genital anomalies, and ear anomalies or deafness). Animal models are bringing us closer to a molecular understanding of optic fissure closure.

SUMMARY

Optic fissure closure requires precise orchestration in timing and apposition of two poles of the optic cup. The relative roles of genetics and environment on this process remain elusive. While most cases of coloboma are sporadic, autosomal dominant, autosomal recessive, and X-linked inheritance patterns have been described. Genetically, colobomata demonstrate pleiotropy, heterogeneity, variable expressivity, and reduced penetrance. Coloboma is a complex disorder with a variable prognosis and requires regular examination to optimize visual acuity and to monitor for potential complications.

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.

Cranio-cerebello-cardiac (3C) syndrome: follow-up study of the original patient

In 1987, Ritscher et al. described two sisters with brain malformations of the posterior fossa, congenital heart defects, and similar craniofacial dysmorphisms. Subsequently, more than 20 cases have been reported and the syndrome became known as 3C (cranio-cerebello-cardiac) or Ritscher-Schinzel syndrome. The majority of patients were younger than six years of age at the time of observation. Here we present a follow-up study of one of the two sisters described by Ritscher et al. in 1987. At 21 years of age she is the oldest patient reported to date. We delineate growth, intellectual development, and evolution of her congenital developmental defects. We also provide evidence that the originally reported immune deficiency in this patient is not a primary B-cell defect but a secondary loss of IgG via the gastrointestinal system.