An unusual presentation of Kabuki syndrome with orbital cysts, microphthalmia, and cholestasis with bile duct paucity

Diagnostic algorithm for neonatal intrahepatic cholestasis integrating single-gene testing and next-generation sequencing in East Asia

BACKGROUND AND AIM

Advances in molecular genetics have uncovered causative genes responsible for neonatal cholestasis. Panel-based next-generation sequencing has been used clinically in infants with neonatal cholestasis. We aimed to evaluate the clinical application of single-gene testing and next-generation sequencing and to develop a diagnostic algorithm for neonatal intrahepatic cholestasis.

METHODS

From January 2010 to July 2021, patients suspected of having neonatal intrahepatic cholestasis were tested at the Seoul National University Hospital. If there was a clinically suspected disease, single-gene testing was performed. Alternatively, if it was clinically difficult to differentiate, a neonatal cholestasis gene panel test containing 34 genes was performed.

RESULTS

Of the total 148 patients examined, 49 (33.1%) were received a confirmed genetic diagnosis, including 14 with Alagille syndrome, 14 with neonatal intrahepatic cholestasis caused by citrin deficiency, 7 with Dubin-Johnson syndrome, 5 with arthrogryposis-renal dysfunction-cholestasis syndrome, 5 with progressive familial intrahepatic cholestasis type II, 1 with Rotor syndrome, 1 with Niemann-Pick disease type C, 1 with Kabuki syndrome, and 1 with Phenylalanyl-tRNA synthetase subunit alpha mutation. Sixteen novel pathogenic or likely pathogenic variants of neonatal cholestasis were observed in this study. Based on the clinical characteristics and laboratory findings, we developed a diagnostic algorithm for neonatal intrahepatic cholestasis by integrating single-gene testing and next-generation sequencing.

CONCLUSIONS

Alagille syndrome and neonatal intrahepatic cholestasis caused by citrin deficiency were the most common diseases associated with genetic neonatal cholestasis. Single-gene testing and next-generation sequencing are important and complementary tools for the diagnosis of genetic neonatal cholestasis.

Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma

BACKGROUND/AIMS

Microphthalmia, anophthalmia and coloboma (MAC) are clinically and genetically heterogenous rare developmental eye conditions, which contribute to a significant proportion of childhood blindness worldwide. Clear understanding of MAC aetiology and comorbidities is essential to providing patients with appropriate care. However, current management is unstandardised and molecular diagnostic rates remain low, particularly in those with unilateral presentation. To further understanding of clinical and genetic management of patients with MAC, we charted their real-world experience to ascertain optimal management pathways and yield from molecular analysis.

METHODS

A prospective cohort study of consecutive patients with MAC referred to the ocular genetics service at Moorfields Eye Hospital between 2017-2020.

RESULTS

Clinical analysis of 50 MAC patients (15 microphthalmia; 2 anophthalmia; 11 coloboma; and 22 mixed) from 44 unrelated families found 44% had additional ocular features (complex) and 34% had systemic involvement, most frequently intellectual/developmental delay (8/17). Molecular analysis of 39 families using targeted gene panels, whole genome sequencing and microarray comparative genomic hybridisation identified genetic causes in, 28% including novel variants in six known MAC genes (SOX2, KMT2D, MAB21L2, ALDH1A3, BCOR and FOXE3), and a molecular diagnostic rate of 33% for both bilateral and unilateral cohorts. New phenotypic associations were found for FOXE3 (bilateral sensorineural hearing loss) and MAB21L2 (unilateral microphthalmia).

CONCLUSION

This study highlights the importance of thorough clinical and molecular phenotyping of MAC patients to provide appropriate multidisciplinary care. Routine genetic testing for both unilateral and bilateral cases in the clinic may increase diagnostic rates in the future, helping elucidate genotype-phenotype correlations and informing genetic counselling.

Molecular insights of KMT2D and clinical aspects of Kabuki syndrome type 1

BACKGROUND

Kabuki syndrome type 1 (KS1), a rare multisystem congenital disorder, presents with characteristic facial features, intellectual disability, persistent fetal fingertip pads, skeletal abnormalities, and postnatal growth delays. KS1 results from pathogenic variants in the KMT2D gene, which encodes a histone methyltransferase protein involved in chromatin remodeling, promoter and enhancer regulation, and scaffold formation during early development. KMT2D also mediates cell signaling pathways, responding to external stimuli and organizing effector protein assembly. Research on KMT2D's molecular mechanisms in KS1 has primarily focused on its histone methyltransferase activity, leaving a gap in understanding the methyltransferase-independent roles in KS1 clinical manifestations.

METHODS

This scoping review examines KMT2D's role in gene expression regulation across various species, cell types, and contexts. We analyzed human pathogenic KMT2D variants using publicly available databases and compared them to research organism models of KS1. We also conducted a systematic search of healthcare and governmental databases for clinical trials, studies, and therapeutic approaches.

RESULTS

Our review highlights KMT2D's critical roles beyond methyltransferase activity in diverse cellular contexts and conditions. We identified six distinct groups of KMT2D as a cell signaling mediator, including evidence of methyltransferase-dependent and -independent activity. A comprehensive search of the literature, clinical databases, and public registries emphasizes the need for basic research on KMT2D's functional complexity and longitudinal studies of KS1 patients to establish objective outcome measurements for therapeutic development.

CONCLUSION

We discuss how KMT2D's role in translating external cellular communication can partly explain the clinical heterogeneity observed in KS1 patients. Additionally, we summarize the current molecular diagnostic approaches and clinical trials targeting KS1. This review is a resource for patient advocacy groups, researchers, and physicians to support KS1 diagnosis and therapeutic development.

Deleterious Variants in ABCC12 are Detected in Idiopathic Chronic Cholestasis and Cause Intrahepatic Bile Duct Loss in Model Organisms

BACKGROUND & AIMS

The etiology of cholestasis remains unknown in many children. We surveyed the genome of children with chronic cholestasis for variants in genes not previously associated with liver disease and validated their biological relevance in zebrafish and murine models.

METHOD

Whole-exome (n = 4) and candidate gene sequencing (n = 89) was completed on 93 children with cholestasis and normal serum γ-glutamyl transferase (GGT) levels without pathogenic variants in genes known to cause low GGT cholestasis such as ABCB11 or ATP8B1. CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 genome editing was used to induce frameshift pathogenic variants in the candidate gene in zebrafish and mice.

RESULTS

In a 1-year-old female patient with normal GGT cholestasis and bile duct paucity, we identified a homozygous truncating pathogenic variant (c.198delA, p.Gly67Alafs∗6) in the ABCC12 gene (NM_033226). Five additional rare ABCC12 variants, including a pathogenic one, were detected in our cohort. ABCC12 encodes multidrug resistance-associated protein 9 (MRP9) that belongs to the adenosine 5'-triphosphate-binding cassette transporter C family with unknown function and no previous implication in liver disease. Immunohistochemistry and Western blotting revealed conserved MRP9 protein expression in the bile ducts in human, mouse, and zebrafish. Zebrafish abcc12-null mutants were prone to cholangiocyte apoptosis, which caused progressive bile duct loss during the juvenile stage. MRP9-deficient mice had fewer well-formed interlobular bile ducts and higher serum alkaline phosphatase levels compared with wild-type mice. They exhibited aggravated cholangiocyte apoptosis, hyperbilirubinemia, and liver fibrosis upon cholic acid challenge.

CONCLUSIONS

Our work connects MRP9 with bile duct homeostasis and cholestatic liver disease for the first time. It identifies a potential therapeutic target to attenuate bile acid-induced cholangiocyte injury.

Ubiquitous Chromatin Modifiers in Congenital Retinal Diseases: Implications for Disease Modeling and Regenerative Medicine

Retinal congenital malformations known as microphthalmia, anophthalmia, and coloboma (MAC) are associated with alterations in genes encoding epigenetic proteins that modify chromatin. We review newly discovered functions of such chromatin modifiers in retinal development and discuss the role of epigenetics in MAC in humans and animal models. Further, we highlight how advances in epigenomic technologies provide foundational and regenerative medicine-related insights into blinding disorders. Combining knowledge of epigenetics and pluripotent stem cells (PSCs) is a promising avenue because epigenetic factors cooperate with eye field transcription factors (EFTFs) to direct PSC fate - a foundation for congenital retinal disease modeling and cell therapy.

Kabuki syndrome: review of the clinical features, diagnosis and epigenetic mechanisms

BACKGROUND

Kabuki syndrome (KS), is a infrequent inherited malformation syndrome caused by mutations in a H3 lysine 4 methylase (KMT2D) or an X-linked histone H3 lysine 27 demethylase (UTX/KDM6A). The characteristics in patients with KS have not yet been well recognized.

DATA SOURCES

We used databases including PubMed and Google Scholar to search for publications about the clinical features and the etiology of Kabuki syndrome. The most relevant articles to the scope of this review were chosen for analysis.

RESULTS

Clinical diagnosis of KS is challenging in initial period, because many clinical characteristics become apparent only in subsequent years. Recently, the genetic and functional interaction between KS-associated genes and their products have been elucidated. New clinical findings were reported including nervous system and intellectual performance, endocrine-related disorders and immune deficiency and autoimmune disease. Cancer risks of Kabuki syndrome was reviewed. Meanwhile, we discussed the Kabuki-like syndrome. Digital clinical genetic service, such as dysmorphology database can improve availability and provide high-quality diagnostic services. Given the significant clinical relevance of KS-associated genes and epigenetic modifications crosstalk, efforts in the research for new mechanisms are thus of maximum interest.

CONCLUSIONS

Kabuki syndrome has a strong clinical and biological heterogeneity. The main pathogenesis of Kabuki syndrome is the imbalance between switch-on and -off of the chromatin. The direction of drug research may be to regulate the normal opening of chromatin. Small molecule inhibitors of histone deacetylases maybe helpful in treatment of mental retardation and reduce cancer risk in KS.

Changes in ocular motility in Kabuki syndrome

Kabuki syndrome is a rare genetic disorder, caused by mutation in the KMT2D or KDM6A genes, which affects several organs in the majority of patients, among which are the eyes. The most typical clinical characteristics are mental retardation, postnatal growth retardation, skeletal anomalies, and characteristic facial features. As the eyes are affected in most of the cases, ophthalmological examination is recommended for the early detection of ocular anomalies, in order to prevent visual impairment. The most frequent ocular signs are strabismus, ptosis, and refractive anomalies. A series of cases of Kabuki syndrome is described in five children, four of whom exhibited strabismus with esotropia, over action of inferior oblique muscles, and under action of superior oblique muscles associated with a V pattern. Most published papers do not report or might underestimate the ocular problems. It may be appropriate to perform orbital magnetic resonances in order to detect changes in the muscle paths that are related to the pathology of the eye movements found.

Cystic biliary atresia with paucity of bile ducts and gene mutation in KDM6A: a case report

Background

Biliary atresia (BA) cases are generally not associated with congenital abnormalities. However, accurate diagnosis of BA is often challenging because the histopathological features of BA overlap with those of other pediatric liver diseases and rarely overlap with those of other genetic disorders. We experienced a rare case of BA with the histopathological finding of bile duct paucity, a gene mutation in KDM6A, and KS-like phenotypes.

Case presentation

A male baby was diagnosed with biliary atresia by intraoperative cholangiography at 4 days of age, and histological examination following a liver biopsy revealed a paucity of bile ducts and several typical clinical findings of Alagille syndrome. However, Alagille syndrome was ruled out after neither JAG1 nor NOTCH2 gene mutations were identified. Whole-exome sequencing on DNA from his parents was additionally performed to examine other possible syndromic disorders, and a mutation was identified in KDM6A. However, Kabuki syndrome was not diagnosed as a result.

The histological finding of interlobular bile duct paucity and the genetic mutation in KDM6A, as well as several clinical findings consistent with Alagille syndrome or Kabuki syndrome, made it difficult to confirm the diagnosis of BA.

Conclusions

Based on the interesting findings of the present case, we hypothesized that KDM6A is associated with hepatic malformations via a connection with the Notch signaling pathway.

The Molecular Basis of Human Anophthalmia and Microphthalmia

Human eye development is coordinated through an extensive network of genetic signalling pathways. Disruption of key regulatory genes in the early stages of eye development can result in aborted eye formation, resulting in an absent eye (anophthalmia) or a small underdeveloped eye (microphthalmia) phenotype. Anophthalmia and microphthalmia (AM) are part of the same clinical spectrum and have high genetic heterogeneity, with >90 identified associated genes. By understanding the roles of these genes in development, including their temporal expression, the phenotypic variation associated with AM can be better understood, improving diagnosis and management. This review describes the genetic and structural basis of eye development, focusing on the function of key genes known to be associated with AM. In addition, we highlight some promising avenues of research involving multiomic approaches and disease modelling with induced pluripotent stem cell (iPSC) technology, which will aid in developing novel therapies.

Genomic medicine for kidney disease

Technologies such as next-generation sequencing and chromosomal microarray have advanced the understanding of the molecular pathogenesis of a variety of renal disorders. Genetic findings are increasingly used to inform the clinical management of many nephropathies, enabling targeted disease surveillance, choice of therapy, and family counselling. Genetic analysis has excellent diagnostic utility in paediatric nephrology, as illustrated by sequencing studies of patients with congenital anomalies of the kidney and urinary tract and steroid-resistant nephrotic syndrome. Although additional investigation is needed, pilot studies suggest that genetic testing can also provide similar diagnostic insight among adult patients. Reaching a genetic diagnosis first involves choosing the appropriate testing modality, as guided by the clinical presentation of the patient and the number of potential genes associated with the suspected nephropathy. Genome-wide sequencing increases diagnostic sensitivity relative to targeted panels, but holds the challenges of identifying causal variants in the vast amount of data generated and interpreting secondary findings. In order to realize the promise of genomic medicine for kidney disease, many technical, logistical, and ethical questions that accompany the implementation of genetic testing in nephrology must be addressed. The creation of evidence-based guidelines for the utilization and implementation of genetic testing in nephrology will help to translate genetic knowledge into improved clinical outcomes for patients with kidney disease.

Carotid artery occlusion in Kabuki syndrome: Case report and literature review

BACKGROUND

Kabuki syndrome is a rare multiple congenital anomaly syndrome whose main diagnostic findings are craniofacial phenotypic changes and mental retardation. Organic structural lesions in the central nervous system are rare, although have been described already. Systemic vascular changes have also been reported rarely.

CASE DESCRIPTION

We report the case of a young patient with Kabuki syndrome who had a transient ischemic attack due to dissection of the internal carotid artery and a likely gliosis area on the white matter.

CONCLUSION

Association of cervical arterial disease with this syndrome has never been described, and its pathophysiology is not yet established; however, it can direct future research and maybe treatment.