Thirdly, both case 20 (de novo) and case 21 (maternally inherited) involved 22q11.1q11.21 duplication affecting the morbid genes TBX1 (MIM: 602054) and CECR2 (MIM: 115470); furthermore, the duplication region partially overlapped with a critical region of cat eye syndrome (CES). The gene discussed is TBX1; the disease is cat-eye syndrome.