HDC and Timothy syndrome: A similar study done by the Tourette International Collaborative Genetics Study (TIC GENETICS), analyzed WES in families with TS and found that histaminergic pathway genes were highly enriched in TS etiology (L-histidine Decarboxylase- HDC enzyme that converts L-histidine to histamine) (18–20), again in line with current models of TS pathophysiology, which involve neurotransmission, inflammation, and smooth muscle tone.