Mutations in both MLC1 and GlialCAM, have been associated with rare megalencephalic leukoencephalopathy with subcortical cysts (MLC1 and 2; prevalence: <1/1000,000), characterized by macrocephaly, developmental delay and seizures that appears in the first years of life (López-Hernández et al., 2011). Here, MLC1 is linked to Global developmental delay.