Neuropsychological profile associated with KAT6A syndrome: Emergent genotype-phenotype trends.

BACKGROUND: KAT6A (Arboleda-Tham) syndrome is a Mendelian disorder of the epigenetic machinery caused by pathogenic variants in the lysine acetyltransferase 6 A (KAT6A) gene. Intellectual disability and speech/language impairment (e.g., minimally verbal) are common features of the disorder, with late-truncating variants associated with a more severe form of intellectual disability. However, much of the cognitive phenotype remains elusive given the dearth of research. PARTICIPANTS AND METHODS: This study examined non-verbal and social skills of 15 individuals with molecularly-confirmed diagnoses of KAT6A syndrome (Mean age = 10.32 years, SD = 4.12). Participants completed select subtests from the DAS-II, the NEPSY-II, and the Beery Buktenica Developmental Test of Visual Motor Integration 6th Edition, and their caregivers completed an assortment of behavior rating inventories. RESULTS: Findings suggest global cognitive impairment with nonverbal cognition scores similar to those for receptive language. Autism-related features, particularly restricted interests and repetitive behaviors, and broad adaptive deficits were common in our sample juxtaposed with a relatively strong social drive and low frequency of internalizing and externalizing behavioral problems. A general trend of lower performance scores on nonverbal and receptive language measures was observed among those with protein-truncating variants vs. missense variants; however, no effect was observed on caregiver rating inventories of daily behaviors. Late and early truncating variants yielded comparable neuropsychological profiles. CONCLUSIONS: Overall, study results show the cognitive phenotype of KAT6A syndrome includes equally impaired nonverbal cognition and receptive language functioning, paired with relatively intact social drive and strengths in behavior regulation. Emergent genotype-phenotype correlations suggest cognition may be more affected in protein-truncating than missense mutations although similar neurobehavioral profiles were observed.

KMT2D Deficiency Causes Sensorineural Hearing Loss in Mice and Humans.

Individuals with Kabuki syndrome type 1 (KS1) often have hearing loss recognized in middle childhood. Current clinical dogma suggests that this phenotype is caused by frequent infections due to the immune deficiency in KS1 and/or secondary to structural abnormalities of the ear. To clarify some aspects of hearing loss, we collected information on hearing status from 21 individuals with KS1 and found that individuals have both sensorineural and conductive hearing loss, with the average age of presentation being 7 years. Our data suggest that while ear infections and structural abnormalities contribute to the observed hearing loss, these factors do not explain all loss. Using a KS1 mouse model, we found hearing abnormalities from hearing onset, as indicated by auditory brainstem response measurements. In contrast to mouse and human data for CHARGE syndrome, a disorder possessing overlapping clinical features with KS and a well-known cause of hearing loss and structural inner ear abnormalities, there are no apparent structural abnormalities of the cochlea in KS1 mice. The KS1 mice also display diminished distortion product otoacoustic emission levels, which suggests outer hair cell dysfunction. Combining these findings, our data suggests that KMT2D dysfunction causes sensorineural hearing loss compounded with external factors, such as infection.

Neurobehavioral phenotype of Kabuki syndrome: Anxiety is a common feature.

Kabuki syndrome (KS) is a Mendelian Disorder of the Epigenetic Machinery (MDEM) caused by loss of function variants in either of two genes involved in the regulation of histone methylation, KMT2D (34-76%) or KDM6A (9-13%). Previously, representative neurobehavioral deficits of KS were recapitulated in a mouse model, emphasizing the role of KMT2D in brain development, specifically in ongoing hippocampal neurogenesis in the granule cell layer of the dentate gyrus. Interestingly, anxiety, a phenotype that has a known association with decreased hippocampal neurogenesis, has been anecdotally reported in individuals with KS. In this study, anxiety and behavior were assessed in a cohort of 60 individuals with molecularly confirmed KS and 25 unaffected biological siblings, via questionnaires (SCARED/GAS-ID and CBCL/ABCL). Participant age ranged from 4 to 43 years old, with 88.3% of participants having a pathogenic variant in KMT2D, and the rest having variants in KDM6A. In addition, data was collected on adaptive function and positive affect/quality of life in participants with KS using appropriate online surveys including ABAS-III and PROMIS Positive Affect. Survey scores were compared within the KS participants across age groups and between KS participants and their unaffected siblings. We found that children with KS have significantly higher anxiety scores and total behavior problem scores than their unaffected siblings (p = 0.0225, p < 0.0001). Moreover, a large proportion of affected individuals (22.2% of children and 60.0% of adults) surpassed the established threshold for anxiety; this may even be an underestimate given many patients are already treated for anxiety. In this sample, anxiety levels did not correlate with level of cognitive or adaptive function in any KS participants, but negatively correlated with positive affect in children with KS (p = 0.0005). These findings indicate that anxiety is a common neurobehavioral feature of KS. Providers should therefore carefully screen individuals with KS for anxiety as well as other behavioral issues in order to allow for prompt intervention. Neurobehavioral anxiety measures may also prove to be important outcome measures for clinical trials in KS.

Sleep disturbance is a common feature of Kabuki syndrome.

Kabuki syndrome (KS) is a rare epigenetic disorder caused by heterozygous loss of function variants in either KMT2D (90%) or KDM6A (10%), both involved in regulation of histone methylation. While sleep disturbance in other Mendelian disorders of the epigenetic machinery has been reported, no study has been conducted on sleep in KS. This study assessed sleep in 59 participants with KS using a validated sleep questionnaire. Participants ranged in age from 4 to 43 years old with 86% of participants having a pathogenic variant in KMT2D. In addition, data on adaptive function, behavior, anxiety, and quality of life were collected using their respective questionnaires. Some form of sleep issue was present in 71% of participants, with night-waking, daytime sleepiness, and sleep onset delay being the most prevalent. Sleep dysfunction was positively correlated with maladaptive behaviors, anxiety levels, and decreasing quality of life. Sleep issues were not correlated with adaptive function. This study establishes sleep disturbance as a common feature of KS. Quantitative sleep measures may be a useful outcome measure for clinical trials in KS. Further, clinicians caring for those with KS should consider sleep dysfunction as an important feature that impacts overall health and well being in these patients.