A region of clinical interest within chromosome 17p13.3 is book-ended by two genes: PAFAH1B1 and YWHAE. Deletion of PAFAH1B1 results in classical lissencephaly (LIS), while larger deletions between PAFAH1B1 and YWHAE, or in other words the MDS critical region, result in MDS (Cardoso et al., 2003; Nagamani et al., 2009). The gene discussed is YWHAE; the disease is Lissencephaly.