Rett and Rett‐like syndrome: Expanding the genetic spectrum to KIF1A and GRIN1 gene.

Background: This study aimed to investigate the new genetic etiologies of Rett syndrome (RTT) or Rett‐like phenotypes. Methods: Targeted next‐generation sequencing (NGS) was performed on 44 Chinese patients with RTT or Rett‐like phenotypes, in whom genetic analysis of MECP2, CDKL5, and FOXG1 was negative. Results: The detection rate was 31.8% (14/44). A de novo pathogenic variant (c.275_276ins AA, p. Cys92*) of KIF1A was identified in a girl with all core features of typical RTT. A patient with atypical RTT was detected having de novo GRIN1 pathogenic variant (c.2337C > A, p. Val793Phe). Additionally, compound heterozygous pathogenic variants of PPT1 gene were detected in a girl, who initially displayed typical RTT features, but progressed into neuronal ceroid lipofuscinoses (NCL) afterwards. Pathogenic variants in KCNQ2, MEF2C, WDR45, TCF4, IQSEC2, and SDHA were also found in our cohort. Conclusions: It is the first time that pathogenic variants of GRIN1 and KIF1A were linked to RTT and Rett‐like profiles. Our findings expanded the genetic heterogeneity of Chinese RTT or Rett‐like patients, and also suggest that some patients with genetic metabolic disease such as NCL, might displayed Rett features initially, and clinical follow‐up is essential for the diagnosis. [ABSTRACT FROM AUTHOR]