CNTNAP2 and Tourette syndrome: Susceptibility genes associated with GTS include: Slit and Trk-like 1 (SLITRK1), L-histidine decarboxylase (HDC), mitochondrial inner membrane protease subunit 2 (IMMP2L), neuroligin 4, X-linked (NLGN4X), and contactin-associated protein 2 (CNTNAP2) [8–12].