THUMPD1 bi-allelic variants cause loss of tRNA acetylation and a syndromic neurodevelopmental disorder.

Covalent tRNA modifications play multi-faceted roles in tRNA stability, folding, and recognition, as well as the rate and fidelity of translation, and other cellular processes such as growth, development, and stress responses. Mutations in genes that are known to regulate tRNA modifications lead to a wide array of phenotypes and diseases including numerous cognitive and neurodevelopmental disorders, highlighting the critical role of tRNA modification in human disease. One such gene, THUMPD1, is involved in regulating tRNA N4-acetylcytidine modification (ac4C), and recently was proposed as a candidate gene for autosomal-recessive intellectual disability. Here, we present 13 individuals from 8 families who harbor rare loss-of-function variants in THUMPD1. Common phenotypic findings included global developmental delay, speech delay, moderate to severe intellectual deficiency, behavioral abnormalities such as angry outbursts, facial dysmorphism, and ophthalmological abnormalities. We demonstrate that the bi-allelic variants identified cause loss of function of THUMPD1 and that this defect results in a loss of ac4C modification in small RNAs, and of individually purified tRNA-Ser-CGA. We further corroborate this effect by showing a loss of tRNA acetylation in two CRISPR-Cas9-generated THUMPD1 KO cell lines. In addition, we also show the resultant amino acid substitution that occurs in a missense THUMPD1 allele identified in an individual with compound heterozygous variants results in a marked decrease in THUMPD1 stability and RNA-binding capacity. Taken together, these results suggest that the lack of tRNA acetylation due to THUMPD1 loss of function results in a syndromic form of intellectual disability associated with developmental delay, behavioral abnormalities, hearing loss, and facial dysmorphism.

Further phenotypic delineation of Alazami syndrome.

Alazami syndrome (AS) is an autosomal recessive condition characterized by the cardinal features of severe growth restriction, moderate to severe intellectual disability, and distinctive facial features. Biallelic pathogenic variants of the LARP7, encoding a chaperone of 7SK noncoding RNA, is implicated in this disease. There are <35 reported cases in the literature. All reported cases share the same three cardinal features of the syndrome. Herein, we report on 12 patients with a confirmed diagnosis of AS from eight unrelated families. The cohort shares the same key feature of the syndrome. Moreover, we report additional phenotypic features, including genito-renal anomalies, ophthalmological abnormalities, and congenital heart disease. Whole-exome sequencing was used in all reported cases, implicating a clinical under-recognition of the syndrome. This report further expands the clinical and molecular characteristics of Alazami syndrome.

Pathogenic STX3 variants affecting the retinal and intestinal transcripts cause an early-onset severe retinal dystrophy in microvillus inclusion disease subjects.

Biallelic STX3 variants were previously reported in five individuals with the severe congenital enteropathy, microvillus inclusion disease (MVID). Here, we provide a significant extension of the phenotypic spectrum caused by STX3 variants. We report ten individuals of diverse geographic origin with biallelic STX3 loss-of-function variants, identified through exome sequencing, single-nucleotide polymorphism array-based homozygosity mapping, and international collaboration. The evaluated individuals all presented with MVID. Eight individuals also displayed early-onset severe retinal dystrophy, i.e., syndromic-intestinal and retinal-disease. These individuals harbored STX3 variants that affected both the retinal and intestinal STX3 transcripts, whereas STX3 variants affected only the intestinal transcript in individuals with solitary MVID. That STX3 is essential for retinal photoreceptor survival was confirmed by the creation of a rod photoreceptor-specific STX3 knockout mouse model which revealed a time-dependent reduction in the number of rod photoreceptors, thinning of the outer nuclear layer, and the eventual loss of both rod and cone photoreceptors. Together, our results provide a link between STX3 loss-of-function variants and a human retinal dystrophy. Depending on the genomic site of a human loss-of-function STX3 variant, it can cause MVID, the novel intestinal-retinal syndrome reported here or, hypothetically, an isolated retinal dystrophy.

Development and validation of an instrument to measure physician awareness of bioethics and medical law in Oman.

BACKGROUND: A different ethos with respect to the perception of medical ethics prevails in societies in transition such as those in the Arabian Peninsula, which makes it difficult to apply international principles of bioethics in medical practice. This study aimed to develop and psychometrically test an instrument that measures physicians' awareness of bioethics and medical law and their attitudes towards the practice of medical ethics. Additionally, it examined physician correlates influencing the awareness of bioethics. METHODS: Following a rigorous review of relevant literature by a panel of experts, a 13-item instrument, the Omani physicians' bioethics and medical law awareness (OBMLA) questionnaire was developed with the aim of assessing physicians' awareness of bioethics and medical law. The study tool's construct validity and internal consistency reliability were examined by exploratory factor analysis (EFA) and Cronbach's alpha. In a cross-sectional study, the questionnaire was distributed among a random sample of 200 physicians at a tertiary hospital in Muscat, Oman. Participant characteristics that may influence awareness of bioethics and medical law were explored. RESULTS: The EFA of the OBMLA questionnaire resulted in three well-loading factors: (1) Physicians' bioethics practice subscale (2) incentive related bioethics subscale and (3) medical law awareness subscale. Internal consistency reliability ranged between Cronbach's α: 0.73-0.8. Of the total 200 participants, 52% reported that teaching medical ethics during medical school was inadequate. The overall mean (standard deviation, SD) of the bioethics awareness score and Omani medical law awareness were 27.6 (3.5) and 10.1 (2.1) respectively. The majority of physicians (73%) reported that they frequently encountered ethical dilemmas in their practice and 24.5% endorsed the view that unethical decisions tended to occur in their practice. CONCLUSION: The study provides an insight into the practice of bioethics, and the awareness of bioethics and medical law among physicians in a teaching hospital in Oman. The OBMLA questionnaire appears to be a valid and reliable tool to assess a physician's awareness of bioethics and medical law. In this preliminary study, it appears that participants have suboptimal scores on the indices which measure practice and awareness of bioethics and medical law.

CNP deficiency causes severe hypomyelinating leukodystrophy in humans.

Myelin pathologies are an important cause of multifactorial, e.g., multiple sclerosis, and Mendelian, e.g., leukodystrophy, neurological disorders. CNP encodes a major component of myelin and its CNS expression is exclusive to myelin-forming oligodendrocytes. Deficiency of CNP in mouse causes a lethal white matter neurodegenerative phenotype. However, a corresponding human phenotype has not been described to date. Here, we describe a multiplex consanguineous family from Oman in which multiple affected members display a remarkably consistent phenotype of neuroregression with profound brain white matter loss. A novel homozygous missense variant in CNP was identified by combined autozygome/exome analysis. Immunoblot analysis suggests that this is a null allele in patient fibroblasts, which display abnormal F-actin organization. Our results suggest the establishment of a novel CNP-related hypomyelinating leukodystrophy in humans.

A novel mutation in DDR2 causing spondylo-meta-epiphyseal dysplasia with short limbs and abnormal calcifications (SMED-SL) results in defective intra-cellular trafficking.

BACKGROUND: The rare autosomal genetic disorder, Spondylo-meta-epiphyseal dysplasia with short limbs and abnormal calcifications (SMED-SL), is reported to be caused by missense or splice site mutations in the human discoidin domain receptor 2 (DDR2) gene. Previously our group has established that trafficking defects and loss of ligand binding are the underlying cellular mechanisms of several SMED-SL causing mutations. Here we report the clinical characteristics of two siblings of consanguineous marriage with suspected SMED-SL and identification of a novel disease-causing mutation in the DDR2 gene. METHODS: Clinical evaluation and radiography were performed to evaluate the patients. All the coding exons and splice sites of the DDR2 gene were sequenced by Sanger sequencing. Subcellular localization of the mutated DDR2 protein was determined by confocal microscopy, deglycosylation assay and Western blotting. DDR2 activity was measured by collagen activation and Western analysis. RESULTS: In addition to the typical features of SMED-SL, one of the patients has an eye phenotype including visual impairment due to optic atrophy. DNA sequencing revealed a novel homozygous dinucleotide deletion mutation (c.2468_2469delCT) on exon 18 of the DDR2 gene in both patients. The mutation resulted in a frameshift leading to an amino acid change at position S823 and a predicted premature termination of translation (p.S823Cfs*2). Subcellular localization of the mutant protein was analyzed in mammalian cell lines, and it was found to be largely retained in the endoplasmic reticulum (ER), which was further supported by its N-glycosylation profile. In keeping with its cellular mis-localization, the mutant protein was found to be deficient in collagen-induced receptor activation, suggesting protein trafficking defects as the major cellular mechanism underlying the loss of DDR2 function in our patients. CONCLUSIONS: Our results indicate that the novel mutation results in defective trafficking of the DDR2 protein leading to loss of function and disease. This confirms our previous findings that DDR2 missense mutations occurring at the kinase domain result in retention of the mutant protein in the ER.

A novel mutation in the NR2E3 gene associated with Goldmann-Favre syndrome and vasoproliferative tumor of the retina.

PURPOSE: Various autosomal recessive retinal dystrophies are reported to be associated with mutations in nuclear receptor subfamily 2, group E, member 3 (NR2E3, also called PNR) gene. The present study proposed to understand the clinical and genetic characteristics of the family of a patient with an ocular phenotype consistent with Goldmann-Favre syndrome (GFS) and vasoproliferative tumors of the retina (VPTRs). METHODS: Twelve family members of the proband from three generations underwent complete ophthalmic examination, including best-corrected visual acuity with Snellen optotypes, tonometry, biomicroscopic examination, indirect ophthalmoscopy after pupillary dilatation, computerized perimetry, optical coherence tomography, fundus photography, intravenous fluorescein angiography, and electroretinography (ERG). All the study subjects underwent genetic analysis of the entire coding region of the NR2E3 gene with the bidirectional DNA sequencing approach. Hundred healthy individuals were screened for the variant. RESULTS: The phenotype of the proband had features of GFS with VPTRs. The tumors showed complete resolution with cryotherapy and transpupillary thermotherapy (TTT). Sequencing of the entire coding region of the NR2E3 gene in the proband revealed a novel homozygous c.1117 A>G variant that led to the amino acid change from aspartic acid to glycine at position 406 (p.D406G). This change was present in the homozygous state in affected family members and in the heterozygous state in unaffected family members, and was undetectable in the control subjects. The identified novel p.D406G homozygous mutation was at an evolutionarily highly conserved region and may possibly affect the protein function (Sorting Intolerant From Tolerant [SIFT] score = 0.00). CONCLUSIONS: Patients with GFS may present with retinal VPTRs that respond to therapy with cryotherapy and TTT. Molecular genetic studies helped to identify a novel p.D406G mutation in the affected members, which will aid in confirming the diagnosis, for genetic counseling of family members and potentially provide some form of therapy for the affected patients.

Pediatric glaucoma terminology.

Glaucoma is a term that refers to many different disorders which may be characterized by age of onset, associated ocular findings, or associated systemic malformations and diseases. Specification of the type of glaucoma, both clinically, and where applicable, molecularly aids in diagnosis, counseling, treatment, and prognosis. The objective of this report is to assist geneticists in understanding glaucoma and recognizing the importance of detailed terminology in clinical genetic diagnosis.

An update on ocular involvement in mucopolysaccharidoses.

PURPOSE OF REVIEW: The purpose of this review is to provide an update on ocular manifestations of mucopolysaccharidoses (MPS), to highlight diagnostic pitfalls in the evaluation of affected patients, and to briefly review etiopathogenesis, systemic manifestations, and therapeutic interventions in MPS. RECENT FINDINGS: Advances in hematopoietic stem cell transplantation and enzyme replacement therapy for MPS have led to decreased morbidity and increased life-span of patients. Besides other causes, visual impairment because of corneal opacification, retinal degeneration, and optic atrophy remains a common cause of disability in MPS. The application of a standard ophthalmic evaluation protocol may serve as an important diagnostic and disease monitoring tool in patients. SUMMARY: Diagnostic delays are not uncommon in patients with MPS. Given the early ocular involvement in MPS, ophthalmologists play a crucial role in early detection and follow-up of patients with MPS. Ophthalmic evaluation can be impeded by corneal opacification and patient cooperation. Altered corneal biomechanics confound intraocular pressure measurements. Recently developed therapies have made early detection increasingly important. Accurate diagnosis of specific MPS subtypes is of paramount importance for initiating appropriate therapy. Combined with advances in supportive care of ocular and systemic manifestations, the prognosis for patients with MPS has vastly improved.

Autosomal Recessive NOTCH3-Related Leukodystrophy in Two Siblings and Review of the Literature.

BACKGROUND: NOTCH3, a large type I transmembrane receptor expressed on arterial smooth muscle cells and capillary pericytes, features a diverse extracellular domain with 34 epidermal growth factor-like repeats. It exhibits distinct phenotypes due to variant zygosity and type; missense mutations cause CADASIL with cerebral vasculopathy, while null mutations lead to severe congenital manifestations. METHODS: This report describes two cases with homozygous loss- of- function variants in NOTCH3 along with their clinical manifestations. RESULTS: These patients presented with a severe congenital phenotype, including eye misalignment, visual impairment, epilepsy, global developmental delay, and subsequent development of pyramidal signs. Biallelic nonsense variants were discovered in both the cases (NM_000435.3:c.2203 C > T (p. [Arg735Ter]). Livedo reticularis was not reported in our cases, although it was present in previously reported patients. Autosomal recessive NOTCH3-related leukodystrophy is usually caused by biallelic null mutations in NOTCH3. CONCLUSIONS: The phenotype of biallelic null variants is associated with a more severe phenotype than the dominantly inherited form of the disease.

Unilateral Proptosis: A Rare Presenting Sign of Acute Myeloid Leukemia.

Unilateral proptosis is a rare initial presenting sign of acute myeloid leukemia (AML). We report a case of unilateral proptosis in a six-year-old girl as the initial manifestation of AML. The cancer link was initially missed and the case was investigated as one of hyperthyroidism. Peripheral blood smear and bone marrow aspirate evaluation showed signs diagnostic of AML. Computed tomography scan of orbits showed infiltrative process in the right orbit, right maxillary, and right ethmoidal sinuses. Unilateral proptosis as an extramedullary first presenting feature of AML is very rare; however, it should always be considered in the differential diagnosis of proptosis in pediatric age group.

Accommodative esotropia: An outcome analysis from a tertiary center in Oman.

AIM: The aim of this study is to determine the outcome of accommodative esotropia (ET) and influencing factors in young Omani children. SUBJECTS AND METHODS: In this retrospective cohort, children diagnosed with accommodative ET who had followed up in a tertiary hospital from 2006 to 2011 were identified. Parameters studied included cycloplegic refraction and its change with time, ocular alignment, binocularity, visual acuity (VA), amblyopia, and requirement for surgery. RESULTS: A total of 51 patients were identified. Twenty-four patients were diagnosed with fully accommodative ET (FAET) and 27 with partially accommodative ET (PAET). The mean (± standard deviation [SD]) age of onset and reporting were 2.6 (±1.58) and 3.2 (±1.84) years in the two groups, respectively. The mean (SD) cycloplegic refraction at presentation was 4.50 (±1.66) in the FAET group and 3.65 (±1.67) in the PAET group. Anisometropia was present in 28% of patients. The mean follow-up period was 4.9 years. The following were detected in the final visit. A reduction in amblyopia from 43% to 6% of patients, binocularity in 75% of patients, and a mean increase of 0.64 (±1.3) D in cycloplegic refraction from the first visit (P = 0.005). The mean angle of deviation at near and distance was 29.86 (±15.21) and 17.80 (±10.14) prism diopters, respectively, in FAET patients and 30.15 (±14.83) and 29.53 (±15.53), respectively, in PAET patients. Thirty-seven percent of the PAET patients underwent surgery within 5 years from diagnosis. All participants in this cohort continued to wear glasses in the last follow-up visit. CONCLUSION: Most children with refractive accommodative ET have an excellent outcome in terms of VA and binocular vision. The PAET group was characterized by delayed reporting, the presence of anisometropia, and lower hypermetropia. Further study is required to determine the possibility of weaning glasses in FAET patients.

Mucolipidosis Type IV in Omani Families with a Novel MCOLN1 Mutation: Search for Evidence of Founder Effect.

Mucolipidosis Type IV (MLIV) is caused by a deficiency of the mucolipin cation channel encoded by Mucolipin TRP Cation Channel 1 gene (MCOLN1). It is a slowly progressive neurodevelopmental and neurodegenerative disorder causing severe psychomotor developmental delay and progressive visual impairment, which is often misdiagnosed as cerebral palsy. We describe six patients with MLIV from two Omani families with a novel c.237+5G>A mutation in the MCOLN1 gene predicted to affect mRNA splicing. Mutation screening with a high-resolution melting (HRM) assay in a large population sample did not detect this mutation in control subjects. This report highlights the importance of considering MLIV in the differential diagnosis of patients in a pediatric age group with cerebral palsy-like presentation. Although the same rare mutation was seen in two apparently unrelated families, this was not seen in the sample screened from the general population. The HRM assay provides a cost-effective assay for population screening for the c.237+5G>A mutation.

Macular cysts in retinal dystrophy.

PURPOSE OF REVIEW: To describe the entity of macular cysts in retinal dystrophy, differentiate it from cystoid macular edema (CME), and review the role of carbonic anhydrase inhibitors in management. RECENT FINDINGS: Macular cysts in retinal dystrophy are seen in retinopathies caused by mutations in the NR2E3 gene, juvenile X-linked retinoschisis (XLRS), and some other retinal dystrophies. These must be distinguished from CME. Optical coherence tomography can clearly demonstrate intraretinal cysts which may not be clinically detectable. Intravenous fluorescein angiography (IVFA) does not show macular hyperfluorescence (i.e. leakage). Molecular genetic testing aids in the diagnosis and elucidation of pathophysiology. Carbonic anhydrase inhibitors may promote resolution of the cysts resulting in visual improvement. SUMMARY: Non-CME macular cysts in retinal dystrophies can be differentiated from CME by a combination of clinical examination, IVFA, and molecular genetic testing to identify causative phenotype. Carbonic anhydrase inhibitors may be effective in promoting resolution.

Congenital Eyelid Anomalies: What General Physicians Need To Know.

The eyelids are important structures that maintain the health of the ocular surface and have an important role in facial esthetics. Any interruption in eyelid development can lead to congenital eyelid deformities. Eyelid abnormalities in children may present at birth due to abnormal embryogenesis (congenital) or may occur at a later stage as the child matures (developmental). These abnormalities, in general, can be classified into three different categories depending on the location: malformation of the margins, malformation of the folds, and malformation of the position. Congenital and developmental eyelid abnormalities are among the most challenging problems encountered by ophthalmic reconstructive surgeons. Additional considerations include social factors regarding the patient's self-awareness of their deformities and associated medical issues, which often coexist and maybe multisystem in nature. This article briefly reviews eyelid embryology, the most common congenital eyelid anomalies, and the management options available to address these conditions.

Secondary intracranial hypertension in aplastic anemia: A case report and review of current concepts.

Intracranial hypertension (IH) when detected mandates prompt and appropriate therapy to avoid permanent visual impairment. We report a 7-year-old boy who presented to the emergency services with purpuric rashes and bruises. Peripheral blood smear and bone marrow aspiration confirmed the diagnosis of aplastic anemia. During admission, the child developed headache, nausea, vomiting, and diplopia. Ophthalmic examination revealed intermittent esotropia and bilateral papilledema. The findings on neuroimaging and lumbar puncture led to the diagnosis of secondary IH (SIH). The intracranial pressure normalized on treatment with oral acetazolamide, oral furosemide, and intravenous dexamethasone.

Ophthalmic findings as clues for early diagnosis of Vici syndrome in a neonate.

AIM: To report the earliest diagnosis of Vici syndrome in a three-week-old Omani girl. METHODS: A three-week-old baby girl with blond hair and agenesis of the corpus callosum was born to consanguineous parents. An older sibling with similar findings had died at the age of six months with recurrent seizures and aspiration pneumonia without a diagnosis of the underlying systemic condition. After a standard ophthalmic and comprehensive systemic evaluation, full sequencing of the EPG5 gene was carried out. RESULTS: The findings of bilateral anterior polar cataracts and oculocutaneous albinism in the child with agenesis of corpus callosum raised a suspicion of Vici syndrome. Immunology, neurology, cardiology, and genetic consultations were requested and revealed the presence of immunodeficiency, psychomotor retardation, and hypertrophic cardiomyopathy. Full sequencing of the EPG5 gene led to the detection of a homozygous c.6084 G > A (Trp2028Ter) mutation, confirming the diagnosis of Vici syndrome. Parental heterozygosity was confirmed. On follow-up, progressive microcephaly, failure to thrive, and significant developmental delay were noted, and a clinical decision not to resuscitate was made at the age of 22 months. CONCLUSIONS: We report the earliest diagnosis of Vici syndrome in the literature. Ophthalmic findings are a cardinal feature of this condition. The diagnosis should be considered in infants with hallmark features of oculocutaneous albinism, cataracts, and agenesis of the corpus callosum. Vici syndrome has a very poor prognosis due to progressive neuroregression superimposed on the neurodevelopmental anomaly.

Chronic myelogenous leukemia in a child following treatment for bilateral retinoblastoma.

A 3-year-old child was incidentally found to have chronic myelogenous leukemia (CML) during an admission for a routine ophthalmic examination under anesthesia. The child had received systemic chemotherapy and focal treatment for Groups C and D retinoblastoma in the right and left eye, respectively, when she was 7 months old. CML was treated with dasatinib, and the child attained a major molecular response. The child is now 3 years after treatment of CML, and the retinoblastoma remains inactive. CML following treatment of retinoblastoma is a rare occurrence. Long term and close monitoring of retinoblastoma patients who received systemic chemotherapy using serial blood tests is essential.

Molecular analysis of CYP1B1 in Omani patients with primary congenital glaucoma: a pilot study.

PURPOSE: To screen cytochrome P4501B1 (CYP1B1) for causative mutations in Omani patients with a clinical diagnosis of primary congenital glaucoma (PCG) METHODS: Nine PCG families were recruited for the study. All patients underwent detailed clinical examinations to confirm the diagnosis of PCG. The families of index patients were also examined. Genealogical information was obtained by pedigree analysis. The primary candidate gene, CYP1B1, was amplified from genomic DNA, sequenced, and analyzed in patients to identify the disease-causing mutations. RESULTS: Eight of the nine PCG families were consanguineous (89%). Molecular analysis of CYP1B1 showed three distinct mutations, p.G61E, p.D374N, and p.R368H, in seven of nine unrelated PCG index patients (78%). Six patients had homozygous mutations and one had a compound heterozygous mutation. Causative mutations were not identified in two families. In family 4, the index patient was found to be heterozygous for the p.E229K variant. In family 6, although affected individuals were found to be homozygous in the CYP1B1 region, no mutation could be identified. CONCLUSIONS: This study indicates that CYP1B1 could be the predominant cause of PCG in the Omani population (78%). Omani PCG patients show allelic heterogeneity. Further studies are needed to delineate the spectrum of CYP1B1mutations in Omani PCG families and to identify new or modifier genes contributing to the manifestations of PCG in this region.

Visual rehabilitation by scleral fixation of posterior chamber intraocular lenses in Omani children with aphakia.

BACKGROUND AND OBJECTIVE: To report indications and outcomes of scleral-fixated posterior chamber intraocular lenses (PC IOLs) in Omani children with aphakia. PATIENTS AND METHODS: Patients with aphakia who were younger than 16 years, unsuitable for spectacle or contact lens correction, and without capsular support underwent an anterior vitrectomy and 10-0 polypropylene inside-out scleral fixation ofa PC IOL. RESULTS: Scleral-fixated PC IOLs were implanted in 28 eyes of 24 patients. Group A comprised 10 (36%) eyes with congenital cataract and 3 (11%) eyes with ectopia lentis and group B comprised 15 (53%) eyes with traumatic cataract. The mean age at implantation was higher in group A (10.5 years) than in group B (7.3 years). Visual acuity improved in 17 of 28 (61%) eyes and remained at the preoperative levels in 11 of 28 (39%) eyes. Mean postoperative refraction was within +/- 2.0 diopters of the predicted refraction in 19 of 28 (68%) eyes. Complications included temporary intraocular pressure increase, vitreous hemorrhage, and iris capture with lens malposition. CONCLUSION: Scleral-fixated PC IOLs are beneficial for children with aphakia without posterior capsular support who are lacking other means for visual rehabilitation. Patients with traumatic cataract and lens dislocation are more likely to experience an improvement in visual acuity postoperatively than patients with congenital cataract. However, this procedure is technically more difficult than routine PC IOL implantation and potentially carries greater risks.