DPP4 and Behcet disease: This study identified two rare mutations, the G327E mutation of SCN9A and the A654V mutation of the DPP4, cosegregating with SZ and BD in the first family and three rare mutations cosegregating with SZ and bipolar in the second family, including L711S mutation of SCN9A, M4554I mutation of ABCA13, and P159L of SYT14.