Expanding the Neuropsychological Phenotype of KAT6B Disorders: Overlapping Features with KAT6A Syndrome.

KAT6B and KAT6A belong to the MYST family of lysine acetyltransferases, and regulate gene expression via histone modification. Although both proteins share similar structure and epigenetic regulatory functions, it remains unclear if KAT6A/6B mutation disorders, both very rare conditions, yield the same neurocognitive presentation and thus benefit from similar treatment approaches. This study provides a preliminary overview of neuropsychological functioning of 13 individuals with KAT6B disorder (Mean age = 9.01 years, SD = 5.46), which was compared to that of a recently published sample of 15 individuals with KAT6A syndrome (Mean age = 10.32 years, SD = 4.12). Participants completed a neuropsychological test battery to assess non-verbal cognition, and caregivers completed a series of standardized rating inventories to assess daily behavioral functioning. Results reveal those with KAT6B disorders present with severe adaptive deficits (92.3%) and autism-related behaviors (83.3%), juxtaposed with relatively low concerns with externalizing behaviors (7.6%), a pattern shared by the KAT6A group. Those with KAT6B disorders present with high levels of autistic features, including reduced affiliative interest, whereas social motivation is less affected within the KAT6A group. Overall, the levels of impairment in nonverbal cognition and receptive language were comparable among those with KAT6B disorders, a trend also seen in the KAT6A group. In brief, KAT6B and KAT6A disorders yield analogous neuropsychological profiles. Findings implicate common molecular pathophysiological mechanisms for these epigenetic disorders, such that similar therapies may have shared effect across diseases.