Most patients with a MECP2 duplication also have an IRAK1 duplication due to the close proximity of the two genes (Sugitate et al. 2022), and the full duplication of both genes may be necessary for the correct diagnosis of MRXSL (Pascual-Alonso et al. 2020). Here, IRAK1 is linked to syndromic X-linked intellectual disability Lubs type.