Thus, to reduce mast cell activity and MCAD-associated increased PBL activity neuropeptide receptor antagonists, acting on the neurokinin-1 receptor for SP or on the Mas-related gene receptor X2, as a common receptor for SP, somatostatin, and VIP [65,68], might be additional promising treatment options in the therapy of MCAD. The gene discussed is TACR1; the disease is medium chain acyl-CoA dehydrogenase deficiency.