DRD4 and Behcet disease: Gene2MeSH-nominated candidates for comorbid BD with TUD include: catechol-O-methyltransferase (COMT, Entrez GeneID 1312); solute carrier family 6 (neurotransmitter transporter, dopamine), member 3 (SLC6A3, GeneID 6531); solute carrier family 6 (neurotransmitter transporter, serotonin), member 4 (SLC6A4, GeneID 6532); tryptophan hydroxylase 1 (TPH1, GeneID 7166); and dopamine receptor D4 (DRD4, GeneID 1815).