Genetic causes of syndromic craniosynostoses

AI-based diagnosis and phenotype - Genotype correlations in syndromic craniosynostoses

Apert (AS), Crouzon (CS), Muenke (MS), Pfeiffer (PS), and Saethre Chotzen (SCS) are among the most frequently diagnosed syndromic craniosynostoses. The aims of this study were (1) to train an innovative model using artificial intelligence (AI)-based methods on two-dimensional facial frontal, lateral, and external ear photographs to assist diagnosis for syndromic craniosynostoses vs controls, and (2) to screen for genotype/phenotype correlations in AS, CS, and PS. We included retrospectively and prospectively, from 1979 to 2023, all frontal and lateral pictures of patients genetically diagnosed with AS, CS, MS, PS and SCS syndromes. After a deep learning-based preprocessing, we extracted geometric and textural features and used XGboost (eXtreme Gradient Boosting) to classify patients. The model was tested on an independent international validation set of genetically confirmed patients and non-syndromic controls. Between 1979 and 2023, we included 2228 frontal and lateral facial photographs corresponding to 541 patients. In all, 70.2% [0.593-0.797] (p < 0.001) of patients in the validation set were correctly diagnosed. Genotypes linked to a splice donor site of FGFR2 in Crouzon-Pfeiffer syndrome (CPS) caused a milder phenotype in CPS. Here we report a new method for the automatic detection of syndromic craniosynostoses using AI.

Prenatal and infantile diagnosis of craniosynostosis in individuals with RASopathies

Fetuses with RASopathies can have a wide variety of anomalies including increased nuchal translucency, hydrops fetalis, and structural anomalies (typically cardiac and renal). There are few reports that describe prenatal-onset craniosynostosis in association with a RASopathy diagnosis. We present clinical and molecular characteristics of five individuals with RASopathy and craniosynostosis. Two were diagnosed with craniosynostosis prenatally, 1 was diagnosed as a neonate, and 2 had evidence of craniosynostosis noted as neonates without formal diagnosis until later. Two of these individuals have Noonan syndrome (PTPN11 and KRAS variants) and three individuals have Cardiofaciocutaneous syndrome (KRAS variants). Three individuals had single suture synostosis and two had multiple suture involvement. The most common sutures involved were sagittal (n = 3), followed by coronal (n = 3), and lambdoid (n = 2) sutures. This case series confirms craniosynostosis as one of the prenatal findings in individuals with RASopathies and emphasizes the importance of considering a RASopathy diagnosis in fetuses with multiple anomalies in combination with craniosynostosis.

Case report: A girl with witnessed sleep apnea

Introduction

Pfeiffer syndrome is a rare genetic disorder characterized by craniosynostosis, broad thumbs and big toes, and partial syndactyly of the hands and feet. This case report presents the case of a girl diagnosed with type 2 Pfeiffer syndrome who experienced severe obstructive sleep apnea (OSA).

Case report

The patient had been using an oropharyngeal airway since the age of 4 months due to snoring and witnessed apnea during sleep. At 11 months old, she was referred to our sleep clinic because of growth limitation and gross motor ability issues. Polysomnography (PSG) showed severe obstructive hypopnea before any treatment, and revealed severe central sleep apnea with the oropharyngeal airway in place. Positive airway pressure (PAP) therapy was initiated, which improved both her sleep and gross motor ability.

Conclusion

This case report emphasizes the importance of thorough sleep studies for diagnosing sleep and breathing disorders in Pfeiffer syndrome patients and highlights the effectiveness of PAP therapy in managing these conditions.

Craniofacial morphology in Apert syndrome: a systematic review and meta-analysis

This meta-analysis aims to compare Apert syndrome (AS) patients with non-AS populations (not clinically or genetically diagnosed) on craniofacial cephalometric characteristics (CCC) to combine publicly available scientific information while also improving the validity of primary study findings. A comprehensive search was performed in the following databases: PubMed, Google Scholar, Scopus, Medline, and Web of Science, an article published between 1st January 2000 to October 17th, 2021. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed to carry out this systematic review. We used the PECO system to classify people with AS based on whether or not they had distinctive CCC compared to the non-AS population. Following are some examples of how PECO has been used: People with AS are labeled P; clinical or genetic diagnosis of AS is labeled E; individuals without AS are labeled C; CCC of AS are labeled O. Using the Newcastle-Ottawa Quality-Assessment-Scale, independent reviewers assessed the articles' methodological quality and extracted data. 13 studies were included in the systematic review. 8 out of 13 studies were score 7-8 in NOS scale, which indicated that most of the studies were medium to high qualities. Six case-control studies were analyzed for meta-analysis. Due to the wide range of variability in CCC, we were only able to include data from at least three previous studies. There was a statistically significant difference in N-S-PP (I2: 76.56%; P = 0.014; CI 1.27 to - 0.28) and Greater wing angle (I2: 79.07%; P = 0.008; CI 3.07-1.17) between AS and control subjects. Cleft palate, anterior open bite, crowding in the upper jaw, and hypodontia occurred more frequently among AS patients. Significant shortening of the mandibular width, height and length is the most reported feature in AS patients. CT scans can help patients with AS decide whether to pursue orthodontic treatment alone or to have their mouth surgically expanded. The role of well-informed orthodontic and maxillofacial practitioners is critical in preventing and rehabilitating oral health issues.

Gli1+ Mesenchymal Stem Cells in Bone and Teeth

Mesenchymal stem cells (MSCs) are remarkable and noteworthy. Identification of markers for MSCs enables the study of their niche in vivo. It has been identified that glioma-associated oncogene 1 positive (Gli1+) cells are mesenchymal stem cells supporting homeostasis and injury repair, especially in the skeletal system and teeth. This review outlines the role of Gli1+ cells as an MSC subpopulation in both bones and teeth, suggesting the prospects of Gli1+ cells in stem cell-based tissue engineering.

Atypical Skin Manifestations in FGFR2-Related Craniosynostosis Syndromes Broaden the Phenotypic Spectrum

Crouzon syndrome (CS) and Beare-Stevenson syndrome (BSS) are craniosynostosis syndromes caused by mutations in the fibroblast growth factor 2 (FGFR2) gene. CS is more common (1 in 60,000 live births) than BSS, where fewer than 20 individuals have been reported. The cardinal features of BSS are craniosynostosis, cutis gyrata, acanthosis nigricans, skin furrows, skin tags, anogenital anomalies, and a prominent umbilical stump. Previously described individuals with BSS have typically had mutations in exon 11 of FGFR2. Here, we present 2 patients with CS who have significant skin manifestations and some phenotypic overlap with BSS. De novo mutations in exon 8 of FGFR2 were identified in both; one is a mutation (c.799T>C; p.Ser267Pro) previously identified in individuals with CS and the other a novel in-frame deletion (c.820_824delinsTT; p.Val274_Glu275delinsLeu). No mutations in exon 11 of FGFR2, where previously reported BSS mutations have been located, were identified. This case expands the phenotypic spectrum of CS and highlights the overlap between conditions caused by mutations in FGFR2.

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.

Endoscopic surgery for patients with syndromic craniosynostosis and the requirement for additional open surgery

OBJECTIVE Recent reports have described early endoscopic suturectomy as a treatment option for patients with syndromic craniosynostosis, but such patients often require subsequent calvarial remodeling. The authors describe their experience with this patient population and seek to identify predictors of sufficiency of endoscopic surgery alone. METHODS The medical records of patients with syndromic craniosynostosis who underwent endoscopic repair were retrospectively reviewed. Demographic data, operative details, and follow-up data were collected. RESULTS A total of 6 patients with syndromic craniosynostosis underwent endoscopic surgery followed by helmet therapy during the study period. Of these, 3 patients were male. The involved syndromes included Crouzon, Pfeiffer, Jackson-Weiss, Muenke, Saethre-Chotzen, and craniosynostosis-3 (n = 1 each). The patients underwent endoscopic surgery at a median age of 2.1 months (range 0.9-4.1 months). The median estimated blood loss was 30 ml (range 20-100 ml), with 2 patients requiring a transfusion. The median length of stay in the hospital was 1.5 days (range 1-4 days), and the median follow-up was 29.0 months (range 16.8-81.7 months), with 1 patient (16.7%) requiring an open revision. Three patients (50%) were classified as Whitaker Category I at the last follow-up. The patients for whom additional open surgery was performed or recommended (Whitaker Category IV) were the oldest patients in the cohort, ranging from 2.6 to 4.1 months at the time of surgery. CONCLUSIONS This series demonstrates that endoscopic surgery can be sufficient to treat syndromic craniosynostosis without subsequent open calvarial remodeling over a median follow-up period of at least 2 years. The findings suggest that younger age at the time of endoscopic surgery may be an important factor in determining the sufficiency of this procedure. Even among patients who require subsequent open calvarial remodeling, early endoscopic surgery may allow for growth and development of the brain and skull while delaying the need for open remodeling until the patient is older and can better tolerate the procedure.

Endoscopic-assisted treatment of sagittal craniosynostosis and calcified cephalohematoma

Craniosynostosis and its associated abnormalities can pose unique challenges to surgeons caring for these patients. Cephalohematomas, although rare, add to the complexities of managing a patient with craniosynostosis. Here, we present the case of a 4-month-old male infant with concurrent sagittal craniosynostosis and a calcified cephalohematoma who underwent an endoscopic-assisted strip craniectomy and management of the hematoma with good results.

The suture provides a niche for mesenchymal stem cells of craniofacial bones

Bone tissue undergoes constant turnover supported by stem cells. Recent studies showed that perivascular mesenchymal stem cells (MSCs) contribute to the turnover of long bones. Craniofacial bones are flat bones derived from a different embryonic origin than the long bones. The identity and regulating niche for craniofacial-bone MSCs remain unknown. Here, we identify Gli1+ cells within the suture mesenchyme as the main MSC population for craniofacial bones. They are not associated with vasculature, give rise to all craniofacial bones in the adult and are activated during injury repair. Gli1+ cells are typical MSCs in vitro. Ablation of Gli1+ cells leads to craniosynostosis and arrest of skull growth, indicating that these cells are an indispensable stem cell population. Twist1(+/-) mice with craniosynostosis show reduced Gli1+ MSCs in sutures, suggesting that craniosynostosis may result from diminished suture stem cells. Our study indicates that craniofacial sutures provide a unique niche for MSCs for craniofacial bone homeostasis and repair.

Facing up to the challenges of advancing Craniofacial Research

Craniofacial anomalies are among the most common human birth defects and have considerable functional, aesthetic, and social consequences. The early developmental origin as well as the anatomical complexity of the head and face render these tissues prone to genetic and environmental insult. The establishment of craniofacial clinics offering comprehensive care for craniofacial patients at a single site together with international research networks focused on the origins and treatment of craniofacial disorders has led to tremendous advances in our understanding of the etiology and pathogenesis of congenital craniofacial anomalies. However, the genetic, environmental, and developmental sources of many craniofacial disorders remain unknown. To overcome this problem and further advance craniofacial research, we must recognize current challenges in the field and establish priority areas for study. We still need (i) a deeper understanding of variation during normal development and within the context of any disorder, (ii) improved genotyping and phenotyping and understanding of the impact of epigenetics, (iii) continued development of animal models and functional analyses of genes and variants, and (iv) integration of patient derived cells and tissues together with 3D printing and quantitative assessment of surgical outcomes for improved practice. Only with fundamental advances in each of these areas will we be able to meet the challenge of translating potential therapeutic and preventative approaches into clinical solutions and reduce the financial and emotional burden of craniofacial anomalies.

Insights into morphology and disease from the dog genome project

Although most modern dog breeds are less than 200 years old, the symbiosis between man and dog is ancient. Since prehistoric times, repeated selection events have transformed the wolf into man's guardians, laborers, athletes, and companions. The rapid transformation from pack predator to loyal companion is a feat that is arguably unique among domesticated animals. How this transformation came to pass remained a biological mystery until recently: Within the past decade, the deployment of genomic approaches to study population structure, detect signatures of selection, and identify genetic variants that underlie canine phenotypes is ushering into focus novel biological mechanisms that make dogs remarkable. Ironically, the very practices responsible for breed formation also spurned morbidity; today, many diseases are correlated with breed identity. In this review, we discuss man's best friend in the context of a genetic model to understand paradigms of heritable phenotypes, both desirable and disadvantageous.