MECP2 and syndromic X-linked intellectual disability Lubs type: MECP2 duplication syndrome (MIM #300260), also known as Lubs-type X-linked syndromic intellectual developmental disorder (MRXSL), is characterized by developmental delay, severe intellectual disability, seizures, poor speech, autistic features, extreme progressive spasticity, gastrointestinal issues, and recurrent infections in males (Pascual-Alonso et al. 2021).