[Clinical and genetic characteristics of X-linked intellectual disability associated with HUWE1 gene variants].

Objective: To explore the clinical and genetic characteristics of X-linked intellectual disability associated with HUWE1 gene variants. Methods: A cases series study retrospectively analyzed the clinical data of 6 children with HUWE1 gene variants. The children were identified from the Third Affiliated Hospital of Zhengzhou University, the First Affiliated Hospital of Zhengzhou University, the First Affiliated Hospital of Henan University of Chinese Medicine, and Guangzhou Women and Children's Medical Center of Guangzhou Medical University between April 2021 and July 2023.The data included sex, age, dysmorphic features, intellectual and motor development, seizure history, neuroimaging findings, family history, and genetic results was analyzed. Results: A total of 6 children, including 5 boys and 1 girl. The age of onset ranged from 1 day to 3 years. All children presented with varying degrees of intellectual disability, with or without motor developmental delay. Dysmorphic features were observed in 4 children, including microcephaly in 3 children. Short stature were observed in 3 children. One child was diagnosed with autism spectrum disorders and 1 child had seizures. Two boys had relevant maternal family histories of febrile seizures and mild intellectual disability, respectively. Abnormal neuroimaging findings were presented in 4 children, including cerebral dysplasia (1 child), prominent supratentorial ventricles (1 child), and mild white matter demyelination (2 children). Whole-exome sequencing identified 5 missense variants and 1 in-frame deletion variant. Five variants were novel and previously unreported (c.12290C>T, c.12701T>C, c.9875C>T, c.9641A>T and c.10313_10315del). The variants in 4 boys were maternally inherited, while the remaining 2 children had de novo variants. The child with the in-frame deletion variant (c.10313_10315del) presented with the most severe phenotype, exhibiting symptoms from 1 day of age, absent cognitive development, feeding difficulties, and congenital laryngeal chondrodysplasia. He was lost to follow-up at 3 months of age after treatment was withdrawn. The age at the last follow-up for the remaining 5 children ranged from 2 years and 10 months to 17 years. A boy with seizures died at 2 years and 10 months of age. The remaining 4 children were able to walk independently at the last follow-up, although their developmental progress was slow. Conclusions: HUWE1 gene related X-linked intellectual disability is characterized by varying degrees of developmental delay and intellectual disability, frequently accompanied by microcephaly, short stature, and occasionally by seizures and autism spectrum disorders. Missense variants are more common and the in-frame deletion variant appears to be associated with a particularly severe phenotypic presentation.