It is known that heterozygous 17p13.3 deletions, including PAFAH1B1 (MIM 601545) and YWHAE (MIM 605066) genes, cause two clinically distinct disorders: LSI (isolated lissencephaly) or MDS (Miller-Dieker syndrome), depending on the size of the deletion[1]. The gene discussed is PAFAH1B1; the disease is lissencephaly spectrum disorders.