In conclusion, we report a Japanese adult and two girls with NEDMIAL caused by missense variants in DHX30. We suggest that NEDMIAL is a novel neurodevelopmental disorder that may mimic Rett syndrome or Angelman syndrome in its early stage, and brain MRI anomalies are pathognomonic findings for the diagnosis of NEDMIAL (Table 1). This evidence concerns the gene DHX30 and Rett syndrome.