The doublecortin gene (DCX) encodes a protein that binds microtubules; it has been implicated in neuronal migration and the development of cerebral cortex. The DCX gene is located at Xq22.3-q23 and contains 10 coding exons. Various types of mutations in the DCX gene have been reported in male patients with lissencephaly, as well as in affected females with subcortical band heteropia (SBH). Affected individuals present with variable degree of epilepsy and mental retardation depending on the degree of agyria (Leger PL et al. Neurogenetics. 2008;9(4):277-85).