Ocular manifestations in Kabuki syndrome: the first report from Saudi Arabia

Macular dystrophy in Kabuki syndrome due to de novo KMT2D variants: refining the phenotype with multimodal imaging and follow-up over 10 years: insight into pathophysiology

BACKGROUND

Kabuki Syndrome is a rare and genetically heterogenous condition with both ophthalmic and systemic complications and typical facial features. We detail the macular phenotype in two unrelated patients with Kabuki syndrome due to de novo nonsense variants in KMT2D, one novel. A follow-up of 10 years is reported. Pathogenicity of both de novo nonsense variants is analyzed.

METHODS

Four eyes of two young patients were studied by full clinical examination, kinetic perimetry, short wavelength autofluorescence, full field (ff) ERGs, and spectral-domain optical coherence tomography (SD-OCT). One patient had adaptive optic (AO) imaging. Whole exome sequencing was performed in both patients.

RESULTS

Both patients had de novo nonsense variants in KMTD2. One patient had c.14843C>G; p. (Ser4948ter) novel variant and the second c.11119C>T; p. (Arg3707ter). Both had a stable Snellen visual acuity of 0.2-0.3. The retinal multimodal imaging demonstrated abnormalities at the fovea in both eyes: hyperreflectivity to blue light and a well-delimited gap-disruption of ellipsoid and interdigitation layer on OCT. The dark area on AO imaging is presumed to be absent for, or with structural change to photoreceptors. The ff ERGs and kinetic visual fields were normal. The foveal findings remained stable over several years.

CONCLUSION

Kabuki syndrome-related maculopathy is a distinct loss of photoreceptors at the fovea as shown by multimodal imaging including, for the first time, AO imaging. This report adds to the literature of only one case with maculopathy with two additional macular dystrophies in patients with Kabuki syndrome. Although underestimated, these cases further raise awareness of the potential impact of retinal manifestations of Kabuki syndrome not only among ophthalmologists but also other healthcare professionals involved in the care of patients with this multisystem disorder.

A Novel Intronic KMT2D Variant as a Cause of Kabuki Syndrome: A Case Report

Kabuki syndrome (KS) is an autosomal dominant genetic disorder in which most cases are caused by de novo mutations. KS type 1 is caused by mutations in KMT2D (OMIM: #147920) and is more common. KS type 2 is caused by mutations in KDM6A (OMIM: #300867). Both genes encode proteins that modify histones and are involved in epigenetic regulation. The enzyme histone-lysine N-methyltransferase 2D, the product of KMT2D, is expressed in most adult tissues and is essential for early embryonic development. The main clinical manifestations of KS include dysmorphic facial features, such as elongated palpebral fissures, eversion of the lateral third of the lower eyelids, and short nasal columella with a broad and depressed nasal tip. Additionally, patients also present with skeletal abnormalities, dermatoglyphic features, mild-to-moderate intellectual disability, hearing loss, and postnatal growth deficiency. We describe an 11-year-old girl from Colombia, who presented with characteristic clinical signs of KS. Genetic studies showed a KMT2D intronic variant (KMT2D NM_003482.3: c.511‐2A> T) as a cause of KS.

Ophthalmic manifestations in Kabuki (make-up) syndrome: A single-center pediatric cohort and systematic review of the literature

Kabuki syndrome (KS) is a genetic disorder caused by pathogenic variants in KMT2D or KDM6A, and manifesting with multi-systemic involvement, including recognizable facial features, developmental delay and multiple congenital anomalies. Ophthalmological involvement has been described in varying rates in several studies. We aimed to evaluate the prevalence and nature of ophthalmological findings in a cohort of KS patients in Israel. Medical records of all patients diagnosed with KS in our tertiary center between 2004 and 2020 were retrospectively reviewed. Data collected included physical examination findings, molecular analysis as well as comprehensive ophthalmic characteristics including visual acuity, ocular alignment and motility, ocular adnexa, anterior segments and dilated fundus exams. Finally, an updated systematic review of the literature was performed. Thirteen unrelated patients were included in the study, diagnosed at an age raging from the first months of life to 20 years. Of these, three (23%) showed significant ophthalmological abnormalities, beyond the characteristic structural findings of long palpebral fissures and lower eyelid eversion. These included bilateral posterior colobomata in the first patient; bilateral ptosis, hypermetropia, esotropia, blue sclera and anisocoria in the second; and bilateral congenital cataracts in the third. To conclude, our findings underscore the importance of a comprehensive ophthalmological evaluation as part of the routine multidisciplinary assessment of children suspected/diagnosed with 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.

Salzmann nodular degeneration features in a case of Kabuki make-up syndrome

Kabuki syndrome (KS) is a multiple congenital anomaly syndrome with diversified ophthalmological manifestations. We report a case of a boy with bilateral features of Salzmann nodular degeneration (SND) associated with KS. An 18-year-old Caucasian man with KS presented for a second opinion regarding incapacitating photophobia in his right eye, refractory to medical therapy. Biomicroscopy revealed bilateral subepithelial nodules in the midperiphery of the cornea, less extensive in the left eye, consistent with SND. Symptomatic improvement was achieved after superficial keratectomy, manually performed with a blade and adjuvant application of mitomycin C. We report a rare case of a KS patient with SND. Since KS manifestations may vary widely, it is important to perform an early ophthalmological examination for prompt detection and treatment of ocular abnormalities and thus improve life quality in these patients.

Kabuki syndrome: expanding the phenotype to include microphthalmia and anophthalmia

Kabuki syndrome is a rare genetic malformation syndrome that is characterized by distinct facies, structural defects and intellectual disability. Kabuki syndrome may be caused by mutations in one of two histone methyltransferase genes: KMT2D and KDM6A. We describe a male child of nonconsanguineous Irish parents presenting with multiple malformations, including bilateral extreme microphthalmia; cleft palate; congenital diaphragmatic hernia; duplex kidney; as well as facial features of Kabuki syndrome, including interrupted eyebrows and lower lid ectropion. A de-novo germline mutation in KMT2D was identified. Whole-exome sequencing failed to reveal mutations in any of the known microphthalmia/anopthalmia genes. We also identified four other patients with Kabuki syndrome and microphthalmia. We postulate that Kabuki syndrome may produce this type of ocular phenotype as a result of extensive interaction between KMT2D, WAR complex proteins and PAXIP1. Children presenting with microphthalmia/anophthalmia should be examined closely for other signs of Kabuki syndrome, especially at an age where the facial gestalt might be less readily appreciable.