KIAA2022-related disorders can cause Jeavons (eyelid myoclonia with absence) syndrome

NEXMIF variants are associated with epilepsy with or without intellectual disability

OBJECTIVES

Variants in NEXMIF had been reported associated with intellectual disability (ID) without epilepsy or developmental epileptic encephalopathy (DEE). It is unkown whether NEXMIF variants are associated with epilepsy without ID. This study aims to explore the phenotypic spectrum of NEXMIF and the genotype-phenotype correlations.

MATERIALS AND METHODS

Trio-based whole-exome sequencing was performed in patients with epilepsy. Previously reported NEXMIF variants were systematically reviewed to analyze the genotype-phenotype correlations.

RESULTS

Six variants were identified in seven unrelated cases with epilepsy, including two de novo null variants and four hemizygous missense variants. The two de novo variants were absent in all populations of gnomAD and four hemizygous missense variants were absent in male controls of gnomAD. The two patients with de novo null variants exhibited severe developmental epileptic encephalopathy. While, the patients with hemizygous missense variants had mild focal epilepsy with favorable outcome. Analysis of previously reported cases revealed that males with missense variants presented significantly higher percentage of normal intellectual development and later onset age of seizure than those with null variants, indicating a genotype-phenotype correlation.

CONCLUSION

This study suggested that NEXMIF variants were potentially associated with pure epilepsy with or without intellectual disability. The spectrum of epileptic phenotypes ranged from the mild epilepsy to severe developmental epileptic encephalopathy, where the epileptic phenotypes variability are potentially associated with patients' gender and variant type.

Dissecting genetics of spectrum of epilepsies with eyelid myoclonia by exome sequencing

OBJECTIVE

Epilepsy with eyelid myoclonia (EEM) spectrum is a generalized form of epilepsy characterized by eyelid myoclonia with or without absences, eye closure-induced seizures with electroencephalographic paroxysms, and photosensitivity. Based on the specific clinical features, age at onset, and familial occurrence, a genetic cause has been postulated. Pathogenic variants in CHD2, SYNGAP1, NEXMIF, RORB, and GABRA1 have been reported in individuals with photosensitivity and eyelid myoclonia, but whether other genes are also involved, or a single gene is uniquely linked with EEM, or its subtypes, is not yet known. We aimed to dissect the genetic etiology of EEM.

METHODS

We studied a cohort of 105 individuals by using whole exome sequencing. Individuals were divided into two groups: EEM- (isolated EEM) and EEM+ (EEM accompanied by intellectual disability [ID] or any other neurodevelopmental/psychiatric disorder).

RESULTS

We identified nine variants classified as pathogenic/likely pathogenic in the entire cohort (8.57%); among these, eight (five in CHD2, one in NEXMIF, one in SYNGAP1, and one in TRIM8) were found in the EEM+ subcohort (28.57%). Only one variant (IFIH1) was found in the EEM- subcohort (1.29%); however, because the phenotype of the proband did not fit with published data, additional evidence is needed before considering IFIH1 variants and EEM- an established association. Burden analysis did not identify any single burdened gene or gene set.

SIGNIFICANCE

Our results suggest that for EEM, as for many other epilepsies, the identification of a genetic cause is more likely with comorbid ID and/or other neurodevelopmental disorders. Pathogenic variants were mostly found in CHD2, and the association of CHD2 with EEM+ can now be considered a reasonable gene-disease association. We provide further evidence to strengthen the association of EEM+ with NEXMIF and SYNGAP1. Possible new associations between EEM+ and TRIM8, and EEM- and IFIH1, are also reported. Although we provide robust evidence for gene variants associated with EEM+, the core genetic etiology of EEM- remains to be elucidated.

Clinical presentation and evaluation of epilepsy with eyelid myoclonia: Results of an international expert consensus panel

OBJECTIVE

The objective of this study was to determine areas of consensus among an international panel of experts for the clinical presentation and diagnosis of epilepsy with eyelid myoclonia (EEM; formerly known as Jeavons syndrome) to improve a timely diagnosis.

METHODS

An international steering committee was convened of physicians and patients/caregivers with expertise in EEM. This committee summarized the current literature and identified an international panel of experts (comprising 25 physicians and five patients/caregivers). This international expert panel participated in a modified Delphi process, including three rounds of surveys to determine areas of consensus for the diagnosis of EEM.

RESULTS

There was a strong consensus that EEM is a female predominant generalized epilepsy syndrome with onset between 3 and 12 years of age and that eyelid myoclonia must be present to make the diagnosis. There was a strong consensus that eyelid myoclonia may go unrecognized for years prior to an epilepsy diagnosis. There was consensus that generalized tonic-clonic and absence seizures are typically or occasionally seen in patients. There was a consensus that atonic or focal seizures should lead to the consideration of reclassification or alternate diagnoses. There was a strong consensus that electroencephalography is required, whereas magnetic resonance imaging is not required for diagnosis. There was a strong consensus to perform genetic testing (either epilepsy gene panel or whole exome sequencing) when one or a combination of factors was present: family history of epilepsy, intellectual disability, or drug-resistant epilepsy.

SIGNIFICANCE

This international expert panel identified multiple areas of consensus regarding the presentation and evaluation of EEM. These areas of consensus may be used to inform clinical practice to shorten the time to the appropriate diagnosis.

A comprehensive narrative review of epilepsy with eyelid myoclonia

Epilepsy with eyelid myoclonia (EEM) is a generalized epilepsy syndrome with childhood-onset and 2:1 female predominance that consists of: 1. eyelid myoclonia with or without absence seizures, 2. eye closure induced seizures or EEG paroxysms, 3. clinical or EEG photosensitivity. While eyelid myoclonia is the disease hallmark, other seizure types, including absence seizures and generalized tonic-clonic seizures, may be present. It is thought to have a genetic etiology, and around one-third of patients may have a positive family history of epilepsy. Recently, specific genetic mutations have been recognized in a minority patients, including in SYNGAP1, NEXMIF, RORB, and CHD2 genes. There are no randomized controlled trials in EEM, and the management literature is largely restricted to small retrospective studies. Broad-spectrum antiseizure medications such as valproate, levetiracetam, lamotrigine, and benzodiazepines are typically used. Seizures typically persist into adulthood, and drug-resistant epilepsy is reported in over 50%.

Cortical and Subcortical Network Dysfunction in a Female Patient With NEXMIF Encephalopathy

The developmental and epileptic encephalopathies (DEE) are the most severe group of epilepsies. Recently, NEXMIF mutations have been shown to cause a DEE in females, characterized by myoclonic–atonic epilepsy and recurrent nonconvulsive status. Here we used advanced neuroimaging techniques in a patient with a novel NEXMIF de novo mutation presenting with recurrent absence status with eyelid myoclonia, to reveal brain structural and functional changes that can bring the clinical phenotype to alteration within specific brain networks. Indeed, the alterations found in the patient involved the visual pericalcarine cortex and the middle frontal gyrus, regions that have been demonstrated to be a core feature in epilepsy phenotypes with visual sensitivity and eyelid myoclonia with absences.

Epilepsy With Eyelid Myoclonia (Jeavons Syndrome)

The purpose of this review is to provide a comprehensive update and highlight the distinct electroclinical features and discuss recent advances in the etiology, pathophysiology, and management strategies of epilepsy with eyelid myoclonia. Recent studies indicate that variations of certain genes including CHD2 (chromodomain helicase DNA-binding protein 2), KCNB1, KIAA2022, and NAA10 may occur in these patients. It has been postulated that the occipital cortex may play a role in the pathophysiology. Recent studies of functional imaging and connectivity of neuronal electrical activity have provided additional evidence to support this hypothesis. The frontal cortex has additionally been implicated, and it has been suggested that the epileptic cortex may extend beyond the occipital cortex to involve the posterior temporal cortex. We update the management strategies and describe tools that may predict seizure persistence. Epilepsy with eyelid myoclonias, or Jeavons syndrome, is an idiopathic generalized epilepsy characterized by the triad of eyelid myoclonia with or without absence seizures, eyelid closure-elicited electroencephalographic (EEG) paroxysms (epileptiform discharges and/or seizures), and photosensitivity. This condition may account for up to 13% of generalized epilepsies. However, it is frequently under-reported and under-recognized. Many of the patients develop medically refractory epilepsy, and seizures tend to persist throughout life.

Candidate Genes for Eyelid Myoclonia with Absences, Review of the Literature

Eyelid myoclonia with absences (EMA), also known as Jeavons syndrome (JS) is a childhood onset epileptic syndrome with manifestations involving a clinical triad of absence seizures with eyelid myoclonia (EM), photosensitivity (PS), and seizures or electroencephalogram (EEG) paroxysms induced by eye closure. Although a genetic contribution to this syndrome is likely and some genetic alterations have been defined in several cases, the genes responsible for have not been identified. In this review, patients diagnosed with EMA (or EMA-like phenotype) with a genetic diagnosis are summarized. Based on this, four genes could be associated to this syndrome (SYNGAP1, KIA02022/NEXMIF, RORB, and CHD2). Moreover, although there is not enough evidence yet to consider them as candidate for EMA, three more genes present also different alterations in some patients with clinical diagnosis of the disease (SLC2A1, NAA10, and KCNB1). Therefore, a possible relationship of these genes with the disease is discussed in this review.

Case Report: A Case of Eyelid Myoclonic Status With Tonic-Clonic Seizure and Literature Review

Eyelid myoclonus with or without absence epilepsy is a rare and usually misdiagnosed disease in the neurology department. It is an idiopathic general epileptic syndrome, the onset period is 6-8 years, and is more common in girls. It is characterized by rapid abnormal eye blinking, accompanied by upward rolling of the eye and slight backward movement of the head, with eye closure sensitivity and photosensitivity. The seizure is frequent and short, dozens or even hundreds of times a day; a small number of patients may have eyelid myoclonus status. We report a patient who visits the hospital for the first time with eyelid myoclonic problem; the patient continued to wink the eyes, eye rolled up, and backward movement of the head, accompanied by impairment of consciousness. Video electroencephalography (VEEG) suggests continued spike slow-wave, polyspike slow-wave. After the patient had 2, 4, 6, 8, 10, 12, and 14 Hz of intermittent photic stimulation (IPS), her seizures and epileptic discharges reduced or stopped. Seven min after giving stimulation at 20 Hz, the child developed an occipital-initiated tonic-clonic seizure, which demonstrated that after sufficient IPS stimulation, the occiput cortex became excited and initiated a brain network, leading to diffuse brain discharge and tonic-clonic seizures. At 1 h after onset, the child developed a nonconvulsive state, with impairment of consciousness despite no eyelid myoclonic movements, and VEEG suggested a large number of epileptic discharges. After 10 min of administrating midazolam, the patient's EEG immediately became normal, and the patient regained consciousness. Therefore, this paper presents an eyelid myoclonus status patient with occipital origin seizure, we recorded the whole course of the disease and the treatment effect, and reviewed the literature accordingly.

RLIM Is a Candidate Dosage-Sensitive Gene for Individuals with Varying Duplications of Xq13, Intellectual Disability, and Distinct Facial Features

Interpretation of the significance of maternally inherited X chromosome variants in males with neurocognitive phenotypes continues to present a challenge to clinical geneticists and diagnostic laboratories. Here we report 14 males from 9 families with duplications at the Xq13.2-q13.3 locus with a common facial phenotype, intellectual disability (ID), distinctive behavioral features, and a seizure disorder in two cases. All tested carrier mothers had normal intelligence. The duplication arose de novo in three mothers where grandparental testing was possible. In one family the duplication segregated with ID across three generations. RLIM is the only gene common to our duplications. However, flanking genes duplicated in some but not all the affected individuals included the brain-expressed genes NEXMIF, SLC16A2, and the long non-coding RNA gene FTX. The contribution of the RLIM-flanking genes to the phenotypes of individuals with different size duplications has not been fully resolved. Missense variants in RLIM have recently been identified to cause X-linked ID in males, with heterozygous females typically having normal intelligence and highly skewed X chromosome inactivation. We detected consistent and significant increase of RLIM mRNA and protein levels in cells derived from seven affected males from five families with the duplication. Subsequent analysis of MDM2, one of the targets of the RLIM E3 ligase activity, showed consistent downregulation in cells from the affected males. All the carrier mothers displayed normal RLIM mRNA levels and had highly skewed X chromosome inactivation. We propose that duplications at Xq13.2-13.3 including RLIM cause a recognizable but mild neurocognitive phenotype in hemizygous males.

NEXMIF encephalopathy: an X-linked disorder with male and female phenotypic patterns

PURPOSE

Pathogenic variants in the X-linked gene NEXMIF (previously KIAA2022) are associated with intellectual disability (ID), autism spectrum disorder, and epilepsy. We aimed to delineate the female and male phenotypic spectrum of NEXMIF encephalopathy.

METHODS

Through an international collaboration, we analyzed the phenotypes and genotypes of 87 patients with NEXMIF encephalopathy.

RESULTS

Sixty-three females and 24 males (46 new patients) with NEXMIF encephalopathy were studied, with 30 novel variants. Phenotypic features included developmental delay/ID in 86/87 (99%), seizures in 71/86 (83%) and multiple comorbidities. Generalized seizures predominated including myoclonic seizures and absence seizures (both 46/70, 66%), absence with eyelid myoclonia (17/70, 24%), and atonic seizures (30/70, 43%). Males had more severe developmental impairment; females had epilepsy more frequently, and varied from unaffected to severely affected. All NEXMIF pathogenic variants led to a premature stop codon or were deleterious structural variants. Most arose de novo, although X-linked segregation occurred for both sexes. Somatic mosaicism occurred in two males and a family with suspected parental mosaicism.

CONCLUSION

NEXMIF encephalopathy is an X-linked, generalized developmental and epileptic encephalopathy characterized by myoclonic-atonic epilepsy overlapping with eyelid myoclonia with absence. Some patients have developmental encephalopathy without epilepsy. Males have more severe developmental impairment. NEXMIF encephalopathy arises due to loss-of-function variants.

Clonazepam as an Effective Treatment for Epilepsy in a Female Patient with NEXMIF Mutation: Case Report

The NEXMIF (KIAA2022) gene is located in the X chromosome, and hemizygous mutations in NEXMIF cause X-linked intellectual disability in male patients. Female patients with heterozygous mutations in NEXMIF also show similar, but milder, intellectual disability. Most female patients demonstrate intractable epilepsy compared with male patients, and the treatment strategy for epilepsy is still uncertain. Thus far, 24 female patients with NEXMIF mutations have been reported. Of these 24 patients, 20 also have epilepsy. Until now, epilepsy has been controlled in only 2 of these female patients. We report a female patient with a heterozygous de novo mutation, NM_001008537.2:c.1123del (p.Glu375Argfs*21), in NEXMIF. The patient showed mild intellectual disability, facial dysmorphism, obesity, generalized tonic-clonic seizures, and nonconvulsive status epilepticus. Sodium valproate was effective but caused secondary amenorrhea. We successfully treated her epilepsy with clonazepam without side effects, indicating that clonazepam might be a good choice to treat epilepsy in patients with NEXMIF mutations.

Clinical spectrum of KIAA2022/NEXMIF pathogenic variants in males and females: Report of three patients from Indian kindred with a review of published patients

BACKGROUND

In the last two decades, with the advent of whole-exome and whole-genome sequencing, supplemented with linkage analysis, more than 150 genes responsible for X-linked intellectual disability have been identified. Some genes like NEXMIF remain an enigmatic entity, as often the carrier females show wide phenotypic diversity ranging from completely asymptomatic to severe intellectual disability and drug-resistant epilepsy.

METHODS

We report three patients with pathogenic NEXMIF variants from an Indian family. All of them had language predominant developmental delay and later progressed to moderate intellectual disability with autistic features. We also reviewed the previously published reports of patients with pathogenic NEXMIF variants.

RESULTS

Together with the presented cases, 45 cases (24 symptomatic females) were identified from 15 relevant research items for analysis. Males have demonstrated a more severe intellectual disability and increasingly delayed walking age, autistic features, central hypotonia, and gastroesophageal reflux. In contrast, females have shown a predominant presentation with drug-resistant epilepsy and mild to moderate intellectual impairment. Notably, the affected females demonstrate a higher incidence of myoclonic, absence, and atonic seizures. The majority of the variants reported are nonsense or frameshift mutations, causing loss of function of the NEXMIF gene, while a considerable proportion possesses chromosomal translocations, microdeletions, and duplications.

CONCLUSIONS

NEXMIF gene mutations should be suspected in all cases of X-linked ID and autism cases in males or even in refractory epilepsy cases in females.

Novel NEXMIF gene pathogenic variant in a female patient with refractory epilepsy and intellectual disability

We identified a novel nonsense de novo pathogenic variant of the NEXMIF gene in a 29 year-old female patient with refractory epilepsy and mild intellectual disability. The patient presented with episodic atypical absence status (AS), the longest duration of her seizures was approximately 36 hr. She also had occasional eyelid myoclonia during absence seizure. EEG highlighted a photosensitivity phenomenon and generalized epileptiform discharges that were induced by eye closure. Whole exome sequencing revealed a novel nonsense pathogenic variant c.1063delC (p.L355*) in exon 3 of the NEXMIF gene. The mRNA expression of NEXMIF in this female patient was below -2 SD from the mean of control group. In addition to adding a novel pathogenic variant type to the NEXMIF variant database and conducting mRNA studies, this report also describes a unique phenotype in a patient with atypical AS associated with a NEXMIF variant. We discuss implications for medication management in similar patients.

Torpedo Maculopathy Associated with NEXMIF Mutation

Mutations in the neurite extension and migration factor (NEXMIF) gene are associated with X-linked intellectual disability. Thus far, all males reported with NEXMIF mutations have mild to profound intellectual disability with varying combinations of autistic features, poor or absent speech, epilepsy, facial dysmorphism, and strabismus. Affected females tend to have milder intellectual disability but severe, drug-resistant epilepsy. Here, we present a 32-month-old boy with a novel de novo frameshift NEXMIF pathogenic variant (p.Glu375ArgfsX21) who has mild motor delay, language delay, autistic features, and strabismus. In addition to these commonly described findings of NEXMIF mutations, his fundus exam revealed a very rare ophthalmologic abnormality, torpedo maculopathy. This finding has not previously been reported with NEXMIF mutation; however, on literature review, 7/15 males with NEXMIF mutations had other ophthalmologic abnormalities. This patient expands the phenotypic spectrum for males with NEXMIF mutations and suggests that NEXMIF may play an important role in ocular development.