Bohring-Opitz (Oberklaid-Danks) syndrome: clinical study, review of the literature, and discussion of possible pathogenesis

Fetal MRI Findings, Etiology, and Outcome in Prenatally Diagnosed Schizencephaly

BACKGROUND AND PURPOSE

Schizencephaly is a rare brain anomaly that is increasingly detected in utero. There are limited data on the etiology and outcomes in fetal schizencephaly to guide work-up and counseling. We aimed to determine the associated imaging findings, etiology, and outcomes in schizencephaly detected in utero.

MATERIALS AND METHODS

This retrospective cohort study included 22 fetuses with a total of 34 schizencephaly defects identified by keyword search of fetal MRI reports from 1996 to 2022 followed by image review. Follow-up fetal and postnatal imaging, when available, was reviewed. Data on demographics, etiology, and outcomes were extracted from the electronic medical record.

RESULTS

The schizencephaly defect was open in 28/34, most common in the MCA territory (23/34), and commonly involved the frontal lobe (16/34). Additional intracranial abnormalities were seen in all fetuses, including other cortical malformations (13/22), abnormal posterior fossa (12/22), abnormal corpus callosum (10/20), and intraparenchymal hemorrhage (9/22). The cause of schizencephaly was classified as secondary (as evidenced by intraparenchymal hemorrhage at schizencephaly, monochorionic twin gestation, infection, or maternal/placental risk factor) in 64% (14/22), potentially genetic in 9% (2/22), and unknown in 27% (6/22). Among those liveborn (n = 8), we observed the following outcomes: postnatal death (1/8), tube feeding (1/7), shunted hydrocephalus (1/7), and epilepsy (4/7). Among those older than 1 year of age, cerebral palsy (4/5) and speech delay or intellectual disability (3/5) were common. Cortical malformations remote from schizencephaly were associated with epilepsy (P = .03). On postnatal imaging, open defects were often involuted (8/11), and there were high rates of new/additional findings (4/6).

CONCLUSIONS

In this cohort, fetal schizencephaly was always associated with additional intracranial abnormalities. In most cases, there was evidence that schizencephaly was likely secondary to prior injury. Imaging characteristics may provide clues regarding neurodevelopmental outcome. Postnatal imaging is crucial in assessing the evolution as well as detection of additional abnormalities.

ASXL1-related Bohring-Optiz syndrome complicated by persistent neonatal pulmonary hypertension and abnormal alveoli formation

Bohring-Opitz syndrome (BOS) is a rare disease with a characteristic facial appearance and limb position. This report describes a case of BOS complicated by persistent pulmonary hypertension of the newborn (PPHN) and formation of abnormal alveoli that was confirmed by autopsy. A female neonate was born by cesarean section at 37 weeks and 2 days of gestation and found to have a nevus flammeus, exophthalmos, abnormal palate, retraction of the mandible, and a posture characteristic of BOS. The patients had severe PPHN requiring inhalation of nitric oxide. Genetic testing revealed a de novo frameshift variant in ASXL1. Autopsy revealed that the lung was at the saccular stage, equivalent to 28-34 weeks of gestation. This is the first report to present pathological evidence of immaturity of the lung that may be associated with PPHN in a patient with BOS caused by a variant in ASXL1.

Intrauterine growth in chromatinopathies: A long road for better understanding and for improving clinical management

BACKGROUND

Chromatinopathies are a heterogeneous group of genetic disorders caused by pathogenic variants in genes coding for chromatin state balance proteins. Remarkably, many of these syndromes present unbalanced postnatal growth, both under- and over-, although little has been described in the literature. Fetal growth measurements are common practice in pregnancy management and values within normal ranges indicate proper intrauterine growth progression; on the contrary, abnormalities in intrauterine fetal growth open the discussion of possible pathogenesis affecting growth even in the postnatal period.

METHODS

Among the numerous chromatinopathies, we have selected six of the most documented in the literature offering evidence about two fetal overgrowth (Sotos and Weaver syndrome) and four fetal undergrowth syndromes (Bohring Opitz, Cornelia de Lange, Floating-Harbor, and Meier Gorlin syndrome), describing their molecular characteristics, maternal biochemical results and early pregnancy findings, prenatal ultrasound findings, and postnatal characteristics.

RESULTS/CONCLUSION

To date, the scarce data in the literature on prenatal findings are few and inconclusive, even though these parameters may contribute to a more rapid and accurate diagnosis, calling for a better and more detailed description of pregnancy findings.

PERCHING syndrome caused by variant gene KLHL7 in the first Iranian patient: a case report study

Introduction and importance

PERCHING syndrome is a condition that affects many parts of the body and is caused by genes passed down from both parents. People with this syndrome have delays in their development, unusual facial features, trouble eating and breathing, slow overall growth, weak muscles, and stiff joints.

Case presentation

The child at the age of 6 months suffered from developmental delay, delayed walking, speech delay, and hypotonia and was referred to the Neurologist. Also, he has an abnormal phenotype. Whole-exome sequencing (WES) revealed a missense variant in the KLHL7 gene at a highly conserved genomic Chr7: 23124718T>G; NM_018846:exon3:c.110T>G:p.Val37Gly.

Clinical discussion

One way to explain the difference in physical characteristics caused by recessive KLHL7 mutations might be related to the person's genetic makeup. However, the genes someone has do not always accurately determine their physical traits.

Conclusion

This report will help us learn more about the different traits and characteristics of Perching syndrome. The authors need to do more research on how proteins work and study more about patients with different characteristics to fully understand this.

Perthes-Like Disorder in a Child with Atypical Bohring-Opitz Syndrome

CASE

Bohring-Opitz syndrome is characterized by facial dysmorphism, intellectual disability, specific upper-limb posturing, and developmental delay. We report a case of 14-year-old girl with bilateral hip pain and loss of mobility. Clinical exome sequencing showed a proband with a heterozygous pathogenic nonsense variant in ASXL1 gene.

CONCLUSION

The Perthes-like clinical and radiological features in the hip and the absence of classical upper-limb features are a new phenotype and hence presented here.

Epigenetic regulation by ASXL1 in myeloid malignancies

Myeloid malignancies are clonal hematopoietic disorders that are comprised of a spectrum of genetically heterogeneous disorders, including myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), chronic myelomonocytic leukemia (CMML), and acute myeloid leukemia (AML). Myeloid malignancies are characterized by excessive proliferation, abnormal self-renewal, and/or differentiation defects of hematopoietic stem cells (HSCs) and myeloid progenitor cells hematopoietic stem/progenitor cells (HSPCs). Myeloid malignancies can be caused by genetic and epigenetic alterations that provoke key cellular functions, such as self-renewal, proliferation, biased lineage commitment, and differentiation. Advances in next-generation sequencing led to the identification of multiple mutations in myeloid neoplasms, and many new gene mutations were identified as key factors in driving the pathogenesis of myeloid malignancies. The polycomb protein ASXL1 was identified to be frequently mutated in all forms of myeloid malignancies, with mutational frequencies of 20%, 43%, 10%, and 20% in MDS, CMML, MPN, and AML, respectively. Significantly, ASXL1 mutations are associated with a poor prognosis in all forms of myeloid malignancies. The fact that ASXL1 mutations are associated with poor prognosis in patients with CMML, MDS, and AML, points to the possibility that ASXL1 mutation is a key factor in the development of myeloid malignancies. This review summarizes the recent advances in understanding myeloid malignancies with a specific focus on ASXL1 mutations.

Clinical findings in 39 individuals with Bohring-Opitz syndrome from a global patient-driven registry with implications for tumor surveillance and recurrence risk

Bohring-Opitz syndrome (BOS) is a rare genetic condition caused by pathogenic variants in ASXL1, which is a gene involved in chromatin regulation. BOS is characterized by severe intellectual disabilities, distinctive facial features, hypertrichosis, facial nevus simplex, severe myopia, a typical posture in infancy, variable anomalies, and feeding issues. Wilms tumor has also been reported in two individuals. We report survey data from the largest known cohort of individuals with BOS with 34 participants from the ASXL Patient-Driven Registry and data on five additional individuals with notable findings. Important or novel findings include hepatoblastoma (n = 1), an additional individual with Wilms tumor, two families with a parent who is mosaic including a pair of siblings, birth weights within the normal range for the majority of participants, as well as presence of craniosynostosis and hernias. Data also include characterization of communication, motor skills, and care level including hospitalization frequency and surgical interventions. No phenotype-genotype correlation could be identified. The ASXL Registry is also presented as a crucial tool for furthering ASXL research and to support the ASXL community.

Germline Abnormalities in DNA Methylation and Histone Modification and Associated Cancer Risk

PURPOSE OF REVIEW

Somatic mutations in DNA methyltransferases and other DNA methylation associated genes have been found in a wide variety of cancers. Germline mutations in these genes have been associated with several rare hereditary disorders. Among the described germline/congenital disorders, neurological dysfunction and/or growth abnormalities appear to be a common phenotype. Here, we outline known germline abnormalities and examine the cancer risks associated with these mutations.

RECENT FINDINGS

The increased use and availability of sequencing techniques in the clinical setting has expanded the identification of germline abnormalities involving DNA methylation machinery. This has provided additional cases to study these rare hereditary disorders and their predisposition to cancer. Studying these syndromes may offer an opportunity to better understand the contribution of these genes in cancer development.

De novo nonsense variant in ASXL3 in a Chinese girl causing Bainbridge-Ropers syndrome: A case report and review of literature

BACKGROUND

Bainbridge-Ropers syndrome (BRPS, OMIM #615485) was first identified in 2013 by Bainbridge et al. and is a neurodevelopment disorder characterized by failure to thrive, facial dysmorphism and severe developmental delay. BRPS is caused by heterozygous loss-of-function (LOF) variants in the additional sex combs-like 3 (ASXL3) gene. Due to the limited specific recognizable features and overlapping symptoms with Bohring-Opitz syndrome (BOS, OMIM #612990), clinical diagnosis of BRPS is challenging.

METHODS

In this study, a 2-year-8-month-old Chinese girl was referred for genetic evaluation of severe developmental delay. The reduced fetal movement was found during the antenatal period and bilateral varus deformity of feet was observed at birth. Whole-exome sequencing and Sanger sequencing were used to detect and confirm the variant.

RESULTS

A novel nonsense variant c.1063G>T (p.E355*) in the ASXL3 gene (NM_030632.3) was identified in the proband and the clinical symptoms were compatible with BRPS. The parents were physical and genetic normal and prenatal diagnosis was requested for her pregnant mother with a negative Sanger sequencing result.

CONCLUSION

The study revealed a de novo LOF variant in the ASXL3 gene and expanded the mutation spectrum for this clinical condition. By performing a literature review, we summarized genetic results and the clinical phenotypes of all BPRSs reported so far. More cases study may help to elucidate the function of the ASXL3 gene may be critical to understand the genetic aetiology of this syndrome and assist in accurate genetic counselling, informed decision making and prenatal diagnosis.

Bohring-Opitz syndrome caused by a novel ASXL1 mutation (c.3762delT) in an IVF baby: A case report

RATIONALE

Bohring-Opitz syndrome is a severe congenital disorder associated with a de novo mutation in the additional sex combs-like 1 (ASXL1) gene, and it is characterized by symptoms that include developmental delay and musculoskeletal and neurological features.

PATIENT CONCERNS

The patient was a girl, an in vitro fertilization (IVF) baby, with delayed motor development, drooling, short stature, slow growth, low muscle tone, image diagnosis of hypoplasia of the corpus callosum, delayed tooth eruption, high palatal arch, adduction of the thumb, drooling, not chewing, excessive joint activity, and ligament relaxation.

DIAGNOSIS

Whole-exome sequencing analysis detected 1 novel disruptive frameshift mutation in ASXL1 in the proband but wild-type ASXL1 in both parents.

INTERVENTIONS

Approximately 1 year of rehabilitation training, which included exercise therapy, toy imitation operation, cognition of daily objects, daily living skills training, gesture language training, oral muscle training, and hand movement training.

OUTCOMES

After approximately 1 year of training, the patient was 3 years old and able to eat normally without drooling. She was able to grasp objects and pick them up after they fell. She was able to grasp small objects and actively played with toys. In addition, she was able to crawl on the floor (at slow speed, with poor initiative), stand with assistance, and walk with assistance; she was unstable when standing unassisted (standing unassisted for 8 seconds at most during training).

LESSON

ASXL1 c.3762delT is a novel mutation that may be caused by IVF. This finding suggests that appropriate gene mutation detection approaches may be necessary for IVF technology.

Self-Induced Bilateral Retinal Detachments and Traumatic Cataracts in a Patient With Bohring-Opitz Syndrome

A 9-year-old female with a history of Bohring-Opitz syndrome (BOS), Down syndrome, and autism initially presented with bilateral cataracts and a total retinal detachment in her left eye secondary to chronic self-injurious behavior. The authors report the first case of self-induced retinal detachment and traumatic cataracts in a patient with BOS. For patients who present with self-injurious behavior, the authors advocate for behavioral modifications at home, including the use of "no-no's," supplemental medication if necessary, and behavioral therapy to reduce the risk of self-induced visual injury. The authors also suggest the use of 25-gauge vitrectomy with silicone oil for retinal detachment repair. Finally, given the high risk of irreversible vision loss from amblyopia and recurrent retinal detachments in children with BOS and self-injurious behavior, the authors recommend regular 2-month interval ophthalmic follow-up. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:400-402.].

Novel truncating mutations in ASXL1 identified in two boys with Bohring-Opitz syndrome

Bohring-Opitz syndrome (BOS, or BOPS) is a rare congenital genetic disorder with multisystem abnormalities characterized by significant craniofacial dysmorphism, feeding difficulties, severe developmental delay, profound intellectual disability, flexion of elbows with ulnar deviation, and flexion of the wrists and metacarpophalangeal joints. Here, we report two Chinese BOS patients with distinctive phenotypes caused by novel truncating mutations. One was a boy aged 5 years 9 months who had a novel c.1049G>A/p.Trp350* mutation in ASXL1 and displayed relatively mild BOS symptoms with autism features. The other was a 16-month-old boy who carried a novel c.2689delC/p.His897Ilefs*11 mutation and displayed typical BOS symptoms. New cases with novel mutations, along with a detailed clinical and molecular analysis are important for a better diagnosis and understanding of BOS.

A de novo Variant of ASXL1 Is Associated With an Atypical Phenotype of Bohring-Opitz Syndrome: Case Report and Literature Review

Bohring-Opitz syndrome (BOS) is a rare genetic disease first reported by Bohring et al. in 1999. With the recent development of exome sequencing (ES), de novo truncating mutations in the additional sex-combs-like 1 (ASXL1) gene have been causally implicated in BOS. Herein, we describe a 7-month-old girl with intrauterine growth restriction, severe pulmonary infection, seizures, and craniofacial abnormalities (microcephaly, micro/retrognathia, hypertelorism, depressed nasal bridge, low-set ears and hypertrichosis) at birth. At a later stage, the patient developed global developmental delay. We performed ES and identified a de novo heterozygous mutation in ASXL1, namely, c.1210C>T/p.R404^*. However, this case did not have trigonocephaly, facial hemangioma, prominent eyes, myopia, BOS posture, or brain abnormalities (enlarged subarachnoid spaces, agenesis of the corpus callosum, moderately enlarged cerebral ventricles, or prominent frontal subarachnoid spaces), which are common characteristics in most patients with BOS-harboring ASXL1 mutations. These new data expand the phenotype of BOS driven by ASXL1 and may assist in more accurately delineating the phenotypes caused by variants of this gene.

Further expanding the clinical phenotype in Bainbridge-Ropers syndrome and dissecting genotype-phenotype correlation in the ASXL3 mutational cluster regions

Bainbridge-Ropers syndrome (BRPS) [OMIM#615485] is a neurodevelopmental disorder, characterized by delayed psychomotor development with generalized hypotonia, intellectual disability with poor or absent speech, feeding difficulties, growth failure, specific craniofacial and minor skeletal features. It was firstly reported in 2013 by Bainbridge et al., who observed a group of individuals sharing overlapping features with Bohring-Opitz syndrome which were caused by pathogenic variant in ASXL1, who indeed carried truncating mutations in ASXL3. To date, 33 cases were described in the literature. BRPS is caused by loss-of-function mutations in ASXL3 which are mostly located in two mutational cluster regions (MCR). The exact molecular mechanism of these mutations resulting in the disease phenotype is still uncertain due to the observation of LOF mutations in healthy population. Here, we report four individuals with BRPS carrying de novo LOF mutations in ASXL3, comparing and summarizing the clinical phenotype of all BRPS reported so far. Furthermore, we try to dissect the genotype-phenotype correlation among the two well reported MCRs in all BRPS from the literature.

A novel PTC mutation in the BTB domain of KLHL7 gene in two patients with Bohring-Opitz syndrome-like features

The bric-a-brac, tramtrack and broad complex (BTB) superfamily of conserved proteins are involved in ubiquitin-proteasome system that contains the Kelch-like (KLHL) gene family. Kelch-like family member 7 (KLHL7), one of the KLHL gene family, consists of one BTB/POZ domain, one BACK domain and five or six Kelch motifs. Numerous variants in KLHL7 gene domains have been reported with Crisponi syndrome/cold-induced sweating syndrome type 1 (CS/CISS1)-like features and retinitis pigmentosa 42, and have recently been identified as causing Bohring-Opitz syndrome (BOS)-like features. We report two siblings with BOS-like phenotype with healthy parents and living in Qazvin province (Central Iran). We performed whole-exome sequencing (WES) on the older patient and Sanger sequencing was carried out for validation of potential causative variants in the close family. A novel homozygous frameshift mutation, p.(Phe83Leufs*3), was identified in the BTB domain of KLHL7 that caused a premature translation-termination codon (PTC) in the two siblings with severe developmental delay, microcephaly, facial dysmorphism, peripheral retinal and optic disc atrophy and cardiac septal defects. Our findings are in agreement with the clinical spectrum of KLHL7 mutations, which are associated with BOS-like features that reports for first time in our population.

Extending the phenotypic spectrum of Bohring-Opitz syndrome: Mild case confirmed by functional studies

Bohring-Opitz syndrome (BOS) has been described as a clinically recognizable genetic syndrome since 1999. Clinical diagnostic criteria were established in 2011 and include microcephaly, trigonocephaly, distinctive craniofacial dysmorphic features, facial nevus flammeus, failure to thrive, and severe developmental delays. The same year, different de novo heterozygous nonsense mutations in the ASXL1 were found in affected individuals. Since then, several cases have been reported confirming the association between this chromatin remodeling gene and BOS. Most affected individuals die in early childhood because of unexplained bradycardia, obstructive apnea, or pulmonary infections. Those that survive usually cannot walk independently and are nonverbal. Some have had success using walkers and braces in late childhood. While few are able to speak, many have been able to express basic needs using communication devices as well as gestures with associated basic vocalizations. In this article, we present a mild case of BOS with a de novo pathogenic mutation c.1720-2A>G (p.I574VfsX22) in ASXL1 detected on whole-exome sequencing and confirmed by functional analysis of the messenger RNA splicing pattern on the patient's fibroblasts. She has typical dysmorphic features and is able to run and walk independently as well as to communicate with basic sign language.

Lethal persistent pulmonary hypertension of the newborn in Bohring-Opitz syndrome

Bohring-Opitz syndrome (BOS) is a rare disease with a number of characteristic features, including hypertelorism, prominent metopic suture, exophthalmos, cleft palate, abnormal posture, and developmental retardation. Here, we report a BOS patient presenting with lethal persistent pulmonary hypertension of the newborn (PPHN) and inspiratory respiratory failure. The female infant was treated with nitric oxide and vasodilator, which did not improve her condition. The inspiratory respiratory failure required management with deep sedation. She died on postnatal day 60 due to progressed heart failure. Whole exome sequencing revealed de novo mutation in the ASXL1 gene, c.1934dupG, p.Gly646TrpfsTer12.

Bohring-Opitz syndrome caused by an ASXL1 mutation inherited from a germline mosaic mother

Bohring-Opitz syndrome (BOS) is characterized clinically by severe developmental delays, microcephaly, failure to thrive, and characteristic facial features (prominent eyes, facial nevus simplex [flammeus], and others). Most patients meeting the clinical criteria for BOS (MIM: 605039) have a de novo nonsense or frameshift variant in ASXL1. We report a case of BOS caused by a pathogenic ASXL1 variant inherited from a germline mosaic mother. The ASXL1 mutation was detected via trio exome sequencing. The sequencing data demonstrated that the variant was inherited maternally but that the maternal variant was underrepresented in comparison to the normal allele. These results suggested maternal mosaicism for the variant. Additional testing on the mother was performed on buccal cell DNA, which was also consistent with mosaicism. The mother had been reported to be healthy and the family history is unremarkable. This is the first report of BOS caused by a mutation inherited from an unaffected, presumed germline mosaic parent. This phenomenon has been reported for other traditionally de novo dominant disorders like CHARGE syndrome and Cornelia de Lange syndrome. This case emphasizes the need for accurate low but non-negative recurrence risk counseling for families with children with BOS and it impacts exome interpretation strategy.

Pathological ASXL1 Mutations and Protein Variants Impair Neural Crest Development

The neural crest (NC) gives rise to a multitude of fetal tissues, and its misregulation is implicated in congenital malformations. Here, we investigated molecular mechanisms pertaining to NC-related symptoms in Bohring-Opitz syndrome (BOS), a developmental disorder linked to mutations in the Polycomb group factor Additional sex combs-like 1 (ASXL1). Genetically edited human pluripotent stem cell lines that were differentiated to NC progenitors and then xenotransplanted into chicken embryos demonstrated an impairment of NC delamination and emigration. Molecular analysis showed that ASXL1 mutations correlated with reduced activation of the transcription factor ZIC1 and the NC gene regulatory network. These findings were supported by differentiation experiments using BOS patient-derived induced pluripotent stem cell lines. Expression of truncated ASXL1 isoforms (amino acids 1-900) recapitulated the NC phenotypes in vitro and in ovo, raising the possibility that truncated ASXL1 variants contribute to BOS pathology. Collectively, we expand the understanding of truncated ASXL1 in BOS and in the human NC.

Double outlet right ventricle and aortopulmonary window in a neonate with Bohring-Opitz (Oberklaid-Danks) syndrome: First case report

Bohring-Opitz syndrome (BOS) is a rare, sporadic genetic disorder, characterized by feeding difficulties, developmental delay, flexion abnormalities, dysmorphic facial features and typical body posture (BOS posture). This syndrome is diagnosed on the basis of distinctive clinical features with or without confirmation by genetic studies. Cardiac abnormalities are seen in almost half of the patients, but are nonspecific. We present a case of a 3-week-old male baby with BOS who was referred to our hospital with congestive heart failure, seizures and failure to thrive. He was diagnosed to have double outlet right ventricle and aortopulmonary window (DORV and APW). To our knowledge, this is the first case of Bohring-Opitz Syndrome ever reported with such clinical presentation.

Two siblings with a novel nonsense variant provide further delineation of the spectrum of recessive KLHL7 diseases

Mutations in Kelch-like family member 7 (KLHL7) have recently been described as a cause of a constellation of clinical findings with descriptions of both a Crisponi syndrome (CS)/cold-induced sweating syndrome type 1 (CISS1)-like, as well as a Bohring-Opitz syndrome (BOS)-like presentation. Here we report two siblings of Guatelmalan descent with a novel homozygous nonsense mutation (p.Arg326*) in KLHL7. These children have multiple dysmorphic features and developmental delay. Interestingly, their clinical traits inconsistently overlap both the CS/CISS1-like and BOS-like phenotypes, and the siblings also have subtle differences from each other, suggesting that clinicians need to be aware of the degree of variability in the presentations of these patients. Still, there is enough in common between patients with recessive KLHL7 mutations to define a novel multisystem disease that features various neurodevelopmental, musculoskeletal, dysmorphic, and other unique components. This report adds to the clinical features and disease-associated variants of the newly-recognized spectrum of KLHL7 mutations, and offers a new description, PERCHING, for the resulting syndrome.

Surveillance Recommendations for Children with Overgrowth Syndromes and Predisposition to Wilms Tumors and Hepatoblastoma

A number of genetic syndromes have been linked to increased risk for Wilms tumor (WT), hepatoblastoma (HB), and other embryonal tumors. Here, we outline these rare syndromes with at least a 1% risk to develop these tumors and recommend uniform tumor screening recommendations for North America. Specifically, for syndromes with increased risk for WT, we recommend renal ultrasounds every 3 months from birth (or the time of diagnosis) through the seventh birthday. For HB, we recommend screening with full abdominal ultrasound and alpha-fetoprotein serum measurements every 3 months from birth (or the time of diagnosis) through the fourth birthday. We recommend that when possible, these patients be evaluated and monitored by cancer predisposition specialists. At this time, these recommendations are not based on the differential risk between different genetic or epigenetic causes for each syndrome, which some European centers have implemented. This differentiated approach largely represents distinct practice environments between the United States and Europe, and these guidelines are designed to be a broad framework within which physicians and families can work together to implement specific screening. Further study is expected to lead to modifications of these recommendations. Clin Cancer Res; 23(13); e115-e22. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Syndromic Craniosynostosis Can Define New Candidate Genes for Suture Development or Result from the Non-specifc Effects of Pleiotropic Genes: Rasopathies and Chromatinopathies as Examples

Craniosynostosis is a heterogeneous condition caused by the premature fusion of cranial sutures, occurring mostly as an isolated anomaly. Pathogenesis of non-syndromic forms of craniosynostosis is largely unknown. In about 15–30% of cases craniosynostosis occurs in association with other physical anomalies and it is referred to as syndromic craniosynostosis. Syndromic forms of craniosynostosis arise from mutations in genes belonging to the Fibroblast Growth Factor Receptor (FGFR) family and the interconnected molecular pathways in most cases. However it can occur in association with other gene variants and with a variety of chromosome abnormalities as well, usually in association with intellectual disability (ID) and additional physical anomalies. Evaluating the molecular properties of the genes undergoing intragenic mutations or copy number variations (CNVs) along with prevalence of craniosynostosis in different conditions and animal models if available, we made an attempt to define two distinct groups of unusual syndromic craniosynostosis, which can reflect direct effects of emerging new candidate genes with roles in suture homeostasis or a non-specific phenotypic manifestation of pleiotropic genes, respectively. RASopathies and 9p23p22.3 deletions are reviewed as examples of conditions in the first group. In particular, we found that craniosynostosis is a relatively common component manifestation of cardio-facio-cutaneous (CFC) syndrome. Chromatinopathies and neurocristopathies are presented as examples of conditions in the second group. We observed that craniosynostosis is uncommon on average in these conditions. It was randomly associated with Kabuki, Koolen-de Vries/KANSL1 haploinsufficiency and Mowat–Wilson syndromes and in KAT6B-related disorders. As an exception, trigonocephaly in Bohring-Opitz syndrome reflects specific molecular properties of the chromatin modifier ASXL1 gene. Surveillance for craniosynostosis in syndromic forms of intellectual disability, as well as ascertainment of genomic CNVs by array-CGH in apparently non-syndromic craniosynostosis is recommended, to allow for improvement of both the clinical outcome of patients and the accurate individual diagnosis.

Bainbridge-Ropers syndrome caused by loss-of-function variants in ASXL3: a recognizable condition

Truncating ASXL3 mutations were first identified in 2013 by Bainbridge et al. as a cause of syndromic intellectual disability in four children with similar phenotypes using whole-exome sequencing. The clinical features - postulated by Bainbridge et al. to be overlapping with Bohring-Opitz syndrome - were developmental delay, severe feeding difficulties, failure to thrive and neurological abnormalities. This condition was included in OMIM as 'Bainbridge-Ropers syndrome' (BRPS, #615485). To date, a total of nine individuals with BRPS have been published in the literature in four reports (Bainbridge et al., Dinwiddie et al, Srivastava et al. and Hori et al.). In this report, we describe six unrelated patients with newly diagnosed heterozygous de novo loss-of-function variants in ASXL3 and concordant clinical features: severe muscular hypotonia with feeding difficulties in infancy, significant motor delay, profound speech impairment, intellectual disability and a characteristic craniofacial phenotype (long face, arched eyebrows with mild synophrys, downslanting palpebral fissures, prominent columella, small alae nasi, high, narrow palate and relatively little facial expression). The majority of key features characteristic for Bohring-Opitz syndrome were absent in our patients (eg, the typical posture of arms, intrauterine growth retardation, microcephaly, trigonocephaly, typical facial gestalt with nevus flammeus of the forehead and exophthalmos). Therefore we emphasize that BRPS syndrome, caused by ASXL3 loss-of-function variants, is a clinically distinct intellectual disability syndrome with a recognizable phenotype distinguishable from that of Bohring-Opitz syndrome.

Loss of Asxl1 Alters Self-Renewal and Cell Fate of Bone Marrow Stromal Cell, Leading to Bohring-Opitz-like Syndrome in Mice

De novo ASXL1 mutations are found in patients with Bohring-Opitz syndrome, a disease with severe developmental defects and early childhood mortality. The underlying pathologic mechanisms remain largely unknown. Using Asxl1-targeted murine models, we found that Asxl1 global loss as well as conditional deletion in osteoblasts and their progenitors led to significant bone loss and a markedly decreased number of bone marrow stromal cells (BMSCs) compared with wild-type littermates. Asxl1^−/− BMSCs displayed impaired self-renewal and skewed differentiation, away from osteoblasts and favoring adipocytes. RNA-sequencing analysis revealed altered expression of genes involved in cell proliferation, skeletal development, and morphogenesis. Furthermore, gene set enrichment analysis showed decreased expression of stem cell self-renewal gene signature, suggesting a role of Asxl1 in regulating the stemness of BMSCs. Importantly, re-introduction of Asxl1 normalized NANOG and OCT4 expression and restored the self-renewal capacity of Asxl1^−/− BMSCs. Our study unveils a pivotal role of ASXL1 in the maintenance of BMSC functions and skeletal development.

•

Asxl1 loss impairs BMSC self-renewal and cell fate

•

Asxl1 loss leads to dramatic bone loss

•

Asxl1 loss alters the expression of genes critical for cell fates of BMSCs

•

Re-introducing Asxl1 restores self-renewal and lineage commitment in Asxl1^−/− BMSCs

Novel splicing mutation in the ASXL3 gene causing Bainbridge-Ropers syndrome

Bainbridge-Ropers syndrome (BRPS) is characterized by severe developmental delay, feeding problems, short stature, characteristic facal appearance including arched eyebrows and anteverted nares, and ulnar deviation of the hands. BRPS is caused by a heterozygous mutation in the additional sex combs-like 3 (ASXL3) gene. We describe a patient with severe developmental delay, feeding problems, short stature, autism, and sleep disturbance with a heterozygous de novo splicing mutation in the ASXL3 gene. Reported disease-causing mutations in ASXL3 are located mostly in the first half of exon 11, analogous to ASXL1 mutations of which result in Bohring-Opitz syndrome (BOS). Our findings suggest that the expression of the truncated ASXL3 protein, including ASXN and ASXH domains, give rise to BRPS, which is distinct from but overlaps with BOS. © 2016 Wiley Periodicals, Inc.

Screening of CD96 and ASXL1 in 11 patients with Opitz C or Bohring-Opitz syndromes

Opitz C trigonocephaly (or Opitz C syndrome, OTCS) and Bohring-Opitz syndrome (BOS or C-like syndrome) are two rare genetic disorders with phenotypic overlap. The genetic causes of these diseases are not understood. However, two genes have been associated with OTCS or BOS with dominantly inherited de novo mutations. Whereas CD96 has been related to OTCS (one case) and to BOS (one case), ASXL1 has been related to BOS only (several cases). In this study we analyze CD96 and ASXL1 in a group of 11 affected individuals, including 2 sibs, 10 of them were diagnosed with OTCS, and one had a BOS phenotype. Exome sequences were available on six patients with OTCS and three parent pairs. Thus, we could analyze the CD96 and ASXL1 sequences in these patients bioinformatically. Sanger sequencing of all exons of CD96 and ASXL1 was carried out in the remaining patients. Detailed scrutiny of the sequences and assessment of variants allowed us to exclude putative pathogenic and private mutations in all but one of the patients. In this patient (with BOS) we identified a de novo mutation in ASXL1 (c.2100dupT). By nature and location within the gene, this mutation resembles those previously described in other BOS patients and we conclude that it may be responsible for the condition. Our results indicate that in 10 of 11, the disease (OTCS or BOS) cannot be explained by small changes in CD96 or ASXL1. However, the cohort is too small to make generalizations about the genetic etiology of these diseases.

Bohring-Opitz syndrome (BOS) with a new ASXL1 pathogenic variant: Review of the most prevalent molecular and phenotypic features of the syndrome

Bohring-Opitz syndrome (BOS) was first described by Bohring et al. [1999]. The authors reported four cases which had several features in common, including a prominent metopic suture, hypertelorism, exophthalmos, cleft lip and palate, limb anomalies, as well as difficulty feeding with severe developmental delays. In almost 50% of cases that meet the clinical criteria for BOS, de novo frameshift and nonsense mutations in the ASXL1 gene have been detected, suggesting that loss of function of this gene is a major cause. We report on the clinical characterization of one young female patient who was evaluated because of severe developmental delays, failure to thrive, and multiple minor anomalies and was clinically diagnosed with BOS. Whole exome sequencing analysis detected one novel disruptive frameshift mutation in the ASXL1 gene and we were also able to confirm the presence of two CFTR mutations associated with her chronic pancreatitis with acute severe breakthrough attacks requiring multiple ICU admissions. This latter complication of pancreatitis further contributed to the complexity of the clinical presentation and represents an independent genetic finding. Our case report emphasizes the importance of highly specific phenotypic characterization of patients with complex phenotypes before proceeding with molecular studies. That approach will lead to more accurate molecular data interpretation and better clinical genetic diagnosis, particularly for those patients with rare, difficult-to-diagnose disorders.

Autoimmune Hepatitis with Distal Renal Tubular Acidosis and Small Bowel Partial Malrotation

Renal tubular acidosis (RTA) is not uncommon in patient with chronic autoimmune hepatitis (AIH), but usually remains latent. Here, we report a case of renal tubular acidosis RTA who presented with AIH. She was also diagnosed to have partial bowel malrotation. A 9-year-old girl, a case of distal RTA, presented with jaundice, abdominal distension and altered sensorium. She was diagnosed to be AIH, which was successfully treated with steroids and azathioprine. Coexistent midgut partial malrotation with volvulus was diagnosed during the treatment. She was treated successfully with anti-tuberculous treatment for cervical lymphadenitis. Autoimmune hepatitis should not be ruled out in each case of RTA presenting with jaundice.

HOW TO CITE THIS ARTICLE

Modi TK, Parikh H, Sadalge A, Gupte A, Bhatt P, Shukla A. Autoimmune Hepatitis with Distal Renal Tubular Acidosis and Small Bowel Partial Malrotation. Euroasian J Hepato-Gastroenterol 2015;5(2):107-109.

Clinical management of patients with ASXL1 mutations and Bohring-Opitz syndrome, emphasizing the need for Wilms tumor surveillance

Bohring-Opitz syndrome is a rare genetic condition characterized by distinctive facial features, variable microcephaly, hypertrichosis, nevus flammeus, severe myopia, unusual posture (flexion at the elbows with ulnar deviation, and flexion of the wrists and metacarpophalangeal joints), severe intellectual disability, and feeding issues. Nine patients with Bohring-Opitz syndrome have been identified as having a mutation in ASXL1. We report on eight previously unpublished patients with Bohring-Opitz syndrome caused by an apparent or confirmed de novo mutation in ASXL1. Of note, two patients developed bilateral Wilms tumors. Somatic mutations in ASXL1 are associated with myeloid malignancies, and these reports emphasize the need for Wilms tumor screening in patients with ASXL1 mutations. We discuss clinical management with a focus on their feeding issues, cyclic vomiting, respiratory infections, insomnia, and tumor predisposition. Many patients are noted to have distinctive personalities (interactive, happy, and curious) and rapid hair growth; features not previously reported.

De novo frameshift mutation in ASXL3 in a patient with global developmental delay, microcephaly, and craniofacial anomalies

Background

Currently, diagnosis of affected individuals with rare genetic disorders can be lengthy and costly, resulting in a diagnostic odyssey and in many patients a definitive molecular diagnosis is never achieved despite extensive clinical investigation. The recent advent and use of genomic medicine has resulted in a paradigm shift in the clinical molecular genetics of rare diseases and has provided insight into the causes of numerous rare genetic conditions. In particular, whole exome and genome sequencing of families has been particularly useful in discovering de novo germline mutations as the cause of both rare diseases and complex disorders.

Case presentation

We present a six year old, nonverbal African American female with microcephaly, autism, global developmental delay, and metopic craniosynostosis. Exome sequencing of the patient and her two parents revealed a heterozygous two base pair de novo deletion, c.1897_1898delCA, p.Gln633ValfsX13 in ASXL3, predicted to result in a frameshift at codon 633 with substitution of a valine for a glutamine and introduction of a premature stop codon.

Conclusions

We provide additional evidence that, truncating and frameshifting mutations in the ASXL3 gene are the cause of a newly recognized disorder characterized by severe global developmental delay, short stature, microcephaly, and craniofacial anomalies. Furthermore, we expand the knowledge about disease causing mutations and the genotype-phenotype relationships in ASXL3 and provide evidence that rare, nonsynonymous, damaging mutations are not associated with developmental delay or microcephaly.

De novo truncating mutations in ASXL3 are associated with a novel clinical phenotype with similarities to Bohring-Opitz syndrome

Background

Molecular diagnostics can resolve locus heterogeneity underlying clinical phenotypes that may otherwise be co-assigned as a specific syndrome based on shared clinical features, and can associate phenotypically diverse diseases to a single locus through allelic affinity. Here we describe an apparently novel syndrome, likely caused by de novo truncating mutations in ASXL3, which shares characteristics with Bohring-Opitz syndrome, a disease associated with de novo truncating mutations in ASXL1.

Methods

We used whole-genome and whole-exome sequencing to interrogate the genomes of four subjects with an undiagnosed syndrome.

Results

Using genome-wide sequencing, we identified heterozygous, de novo truncating mutations in ASXL3, a transcriptional repressor related to ASXL1, in four unrelated probands. We found that these probands shared similar phenotypes, including severe feeding difficulties, failure to thrive, and neurologic abnormalities with significant developmental delay. Further, they showed less phenotypic overlap with patients who had de novo truncating mutations in ASXL1.

Conclusion

We have identified truncating mutations in ASXL3 as the likely cause of a novel syndrome with phenotypic overlap with Bohring-Opitz syndrome.

Two novel patients with Bohring-Opitz syndrome caused by de novo ASXL1 mutations

Bohring-Opitz syndrome (BOS) is a rare condition characterized by facial anomalies, multiple malformations, failure to thrive and severe intellectual disabilities. Recently, the cause was identified on the basis of de novo heterozygous mutations in the ASXL1 gene. We report on two novel cases carrying two previously undescribed mutations (c.2407_2411del5 [p.Q803TfsX17] and c.2893C>T [p.R965X]). These new data further support ASXL1 as cause of BOS and may contribute to a more precise definition of the phenotype caused by the disruption of this gene.