Cardiac conduction abnormalities and congenital immunodeficiency in a child with Kabuki syndrome: case report

Primary immunodeficiency in a patient with Kabuki syndrome

Kabuki syndrome is a well-known disease characterized by postnatal growth failure, dysmorphic facial features, skeletal abnormalities, and mental retardation associated with one of the pathogenic mutations in the KMT2D or KDM6A genes. At least 50% of individuals with Kabuki syndrome tend to develop recurrent infections and immune abnormalities, primarily hypogammaglobulinemia. The article describes the clinical course of resistant infectious syndrome in an 18-month-old child without typical dysmorphic and dermatoglyphic manifestations characteristic of Kabuki syndrome. A long history of resistant bacterial infection, enterocolitis, microcephaly, autistic-like behavior, hyperkinetic disorder, CT scan patterns of granulomatous lymphocytic interstitial lung disease (GLILD), suggested the immunodeficiency as part of a hereditary genetically determined syndrome. At the same time, the patient did not experience hypogammaglobulinemia characteristic of Kabuki syndrome. The upper normal response to previously received vaccination and a polyclonal repertoire of B-lymphocytes indicated the absence of disturbances in the humoral immunity. Immunophenotyping revealed the absence of T-regulatory cells (CD4+CD25++CD127–) as well as effector NK cells (CD16+CD56+CD3–) in the peripheral blood. The significant reduction of CD4+CD3+ T-lymphocytes and CD4+/CD8+ index was observed. In addition, no expression of integrin-beta (CD18) on neutrophils revealed.Conclusion. In children under the age of 2, Kabuki syndrome may present difficulties for clinical diagnosis due to the absence of distinctive phenotypic signs. Patients with mental disorders, congenital malformations, recurrent infections suspected of immunodeficiency should be carried out using molecular genetic exploration, including testing for mutations in the KMT2D and KDM6A.

From Genotype to Phenotype-A Review of Kabuki Syndrome

Kabuki syndrome (KS) is a rare neuro-developmental disorder caused by variants in genes of histone modification, including KMT2D and KDM6A. This review assesses our current understanding of KS, which was originally named Niikawa-Kuroki syndrome, and aims to guide surveillance and medical care of affected individuals as well as identify gaps in knowledge and unmet patient needs. Ovid MEDLINE and EMBASE databases were searched from 1981 to 2021 to identify reports related to genotype and systems-based phenotype characterization of KS. A total of 2418 articles were retrieved, and 152 were included in this review, representing a total of 1369 individuals with KS. Genotype, phenotype, and the developmental and behavioral profile of KS are reviewed. There is a continuous clinical phenotype spectrum associated with KS with notable variability between affected individuals and an emerging genotype-phenotype correlation. The observed clinical variability may be attributable to differences in genotypes and/or unknown genetic and epigenetic factors. Clinical management is symptom oriented, fragmented, and lacks established clinical care standards. Additional research should focus on enhancing understanding of the burden of illness, the impact on quality of life, the adult phenotype, life expectancy and development of standard-of-care guidelines.

Kabuki Syndrome-Clinical Review with Molecular Aspects

Kabuki syndrome (KS) is a rare developmental disorder principally comprised of developmental delay, hypotonia and a clearly defined dysmorphism: elongation of the structures surrounding the eyes, a shortened and depressed nose, thinning of the upper lip and thickening of the lower lip, large and prominent ears, hypertrichosis and scoliosis. Other characteristics include poor physical growth, cardiac, gastrointestinal and renal anomalies as well as variable behavioral issues, including autistic features. De novo or inherited pathogenic/likely pathogenic variants in the KMT2D gene are the most common cause of KS and account for up to 75% of patients. Variants in KDM6A cause up to 5% of cases (X-linked dominant inheritance), while the etiology of about 20% of cases remains unknown. Current KS diagnostic criteria include hypotonia during infancy, developmental delay and/or intellectual disability, typical dysmorphism and confirmed pathogenic/likely pathogenic variant in KMT2D or KDM6A. Care for KS patients includes the control of physical and psychomotor development during childhood, rehabilitation and multi-specialist care. This paper reviews the current clinical knowledge, provides molecular and scientific links and sheds light on the treatment of Kabuki syndrome individuals.

Inhibition of Notch signaling rescues cardiovascular development in Kabuki Syndrome

Kabuki Syndrome patients have a spectrum of congenital disorders, including congenital heart defects, the primary determinant of mortality. Seventy percent of Kabuki Syndrome patients have mutations in the histone methyl-transferase KMT2D. However, the underlying mechanisms that drive these congenital disorders are unknown. Here, we generated and characterized zebrafish kmt2d null mutants that recapitulate the cardinal phenotypic features of Kabuki Syndrome, including microcephaly, palate defects, abnormal ear development, and cardiac defects. The cardiac phenotype consists of a previously unknown vasculogenesis defect that affects endocardium patterning and, consequently, heart ventricle lumen formation. Additionally, zebrafish kmt2d null mutants have angiogenesis defects depicted by abnormal aortic arch development, hyperactive ectopic blood vessel sprouting, and aberrant patterning of the brain vascular plexus. We demonstrate that zebrafish kmt2d null mutants have robust Notch signaling hyperactivation in endocardial and endothelial cells, including increased protein levels of the Notch transcription factor Rbpj. Our zebrafish Kabuki Syndrome model reveals a regulatory link between the Notch pathway and Kmt2d during endothelium and endocardium patterning and shows that pharmacological inhibition of Notch signaling rebalances Rbpj protein levels and rescues the cardiovascular phenotype by enhancing endothelial and endocardial cell proliferation and stabilizing endocardial patterning. Taken together, these findings demonstrate that Kmt2d regulates vasculogenesis and angiogenesis, provide evidence for interactions between Kmt2d and Notch signaling in Kabuki Syndrome, and suggest future directions for clinical research.

Epigenetic control of the immune system: a lesson from Kabuki syndrome

Kabuki syndrome (KS) is a rare multi-systemic disorder characterized by a distinct face, postnatal growth deficiency, mild-to-moderate intellectual disability, skeletal and visceral (mainly cardiovascular, renal, and skeletal) malformations, dermatoglyphic abnormalities. Its cause is related to mutations of two genes: KMT2D (histone-lysine N-methyltransferase 2D) and KDM6A (lysine-specific demethylase 6A), both functioning as epigenetic modulators through histone modifications in the course of embryogenesis and in several biological processes. Epigenetic regulation is defined as the complex of hereditable modifications to DNA and histone proteins that modulates gene expression in the absence of DNA nucleotide sequence changes. Different human disorders are caused by mutations of genes involved in the epigenetic regulation, and not surprisingly, all these share developmental defects, disturbed growth (in excess or defect), multiple congenital organ malformations, and also hematological and immunological defects. In particular, most KS patients show increased susceptibility to infections and have reduced serum immunoglobulin levels, while some suffer also from autoimmune manifestations, such as idiopathic thrombocytopenic purpura, hemolytic anemia, autoimmune thyroiditis, and vitiligo. Herein we review the immunological aspects of KS and propose a novel model to account for the immune dysfunction observed in this condition.

KMT2D regulates specific programs in heart development via histone H3 lysine 4 di-methylation

KMT2D, which encodes a histone H3K4 methyltransferase, has been implicated in human congenital heart disease in the context of Kabuki syndrome. However, its role in heart development is not understood. Here, we demonstrate a requirement for KMT2D in cardiac precursors and cardiomyocytes during cardiogenesis in mice. Gene expression analysis revealed downregulation of ion transport and cell cycle genes, leading to altered calcium handling and cell cycle defects. We further determined that myocardial Kmt2d deletion led to decreased H3K4me1 and H3K4me2 at enhancers and promoters. Finally, we identified KMT2D-bound regions in cardiomyocytes, of which a subset was associated with decreased gene expression and decreased H3K4me2 in mutant hearts. This subset included genes related to ion transport, hypoxia-reoxygenation and cell cycle regulation, suggesting that KMT2D is important for these processes. Our findings indicate that KMT2D is essential for regulating cardiac gene expression during heart development primarily via H3K4 di-methylation.

Highlighted article: Cardiac-specific depletion of the H3K4 methyltransferase KMT2D causes dysregulation of genes associated with cell cycle regulation, ion homeostasis and hypoxia signaling.

Combined immunodeficiency in a 3-year-old boy with 16p11.2 and 20p12.2-11.2 chromosomal duplications

We report for the first time on a 3-year-old boy with paternally inherited 212.85 kb-16p11.2 and 7.8 Mb-20p12.2-11.23 interstitial microduplications associated with having congenital cardiac defect, dysmorphic facial features, and combined T-, B-, and NK cell immunodeficiency. In addition the 7.8 Mb-20p12.2-11.23 microduplication is unique showing novel breakpoints among all partial trisomy/duplication 20p reported to date, narrowing down the critical region for trisomy 20p syndrome.

Pathologic aneurysmal dilation of the ascending aorta and dilation of the main pulmonary artery in patients with Kabuki syndrome: valve-sparing aortic root replacement

We report the aneurysmal dilation of the ascending aorta and the main pulmonary artery in 2 children with Kabuki syndrome. In 1 patient, there was progressive aneurysmal dilation of the ascending aorta necessitating aortoplasty. Histologic examination of the resected aorta revealed disrupted and fragmented elastic fibers in the medial layer, along with mucinous degeneration of the aortic wall. This is the first recognition and report of these findings as part of the Kabuki syndrome.

Chorea associated with antiphospholipid antibodies in a patient with Kabuki syndrome

Kabuki syndrome, OMIM 147920 (KS) is a disorder characterized by multi-system abnormalities. These include physical, neurological, endocrine, and autoimmune abnormalities. Multiple autoimmune abnormalities are described in KS such as immune thrombocytopenic purpura (ITP), vitiligo, thyroiditis, hemolytic anemia, and hypogammaglobulinemia. In this report, we describe a patient with KS with sudden onset chorea associated with the presence of anti-phospholipid antibodies (aPLs) in the serum. Chorea in the presence of aPLs has been well described in the literature both in the presence and absence of antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). This report of APL in a patient with KS adds to the list of autoimmune disorders seen in patients with KS and also strengthens the hypothesis that patients with this syndrome have an increased incidence of immune dysregulation.

Unusual case presentations associated with the CD45 C77G polymorphism

CD45, the leucocyte common antigen, is a haematopoietic cell specific tyrosine phosphatase. Human polymorphic CD45 variants are associated with autoimmune and infectious diseases and alter the phenotype and function of lymphocytes, establishing CD45 as an important regulator of immune function. Here we report four patients with diverse diseases with unusual clinical features. All four have the C77G polymorphism of CD45 exon 4, which alters the splicing and CD45RA/CD45R0 phenotype of lymphocytes. We suggest that C77G may be a contributing factor in these unusual cases.