38, 39 Moreover, in skin biopsies of patients with rosacea, more mast cells express MRGPRX2 than in normal subjects.40 Furthermore, LL-37-induced rosacea in mice was significantly reduced in mast cell deficient KitW-sh/W-sh mice and Mrgprb2−/− mice.40 The gene discussed is MRGPRX2; the disease is rosacea.