The antagonists of the two prostaglandin D2 receptors, prostaglandin D2 receptor 1 (DP1) and chemoattractant homologous receptor expressed on Th2 cells (CRTH2), may theoretically be a future approach to the treatment of tachycardia in MCAD. The gene discussed is PTGDR2; the disease is medium chain acyl-CoA dehydrogenase deficiency.