HDC and Timothy syndrome: Genome‐wide, candidate gene, and CNV studies on TS etiopathogenesis have revealed multiple gene variants, including dopaminergic (DRD2,DRD4,DAT1) (Díaz‐Anzaldúa et al., 2004; Herzberg et al., 2010; Tarnok et al., 2007), serotonergic (HTR1A, HTR2C) (Dehning et al., 2010; Lam et al., 1996), glutamatergic (SLC1A3) (Adamczyk et al., 2011), synapse developmental and functional (SLITRK1, NLGN4, and NRXN1) (Abelson et al., 2005; Lawson‐Yuen et al., 2008; Nag et al., 2013), and neurotransmitter receptor (GRIN2b, HDC) (Ercan‐Sencicek et al., 2010).