L1CAM and lissencephaly spectrum disorders: In our study, we found a NM_000425.5:c.2491del:p.(Val831Serfs*20) variant, located in the exon 19 of L1CAM (chrX:153131214), that could damage the L1CAM function by producing a frameshift in the translation of fibronectin type‐III of L1CAM, resulting in the bilateral ventriculomegaly with dilatation of the third ventricle, polyhydramnios, callosal agenesis, and lissencephaly.