LRRC4 and rosacea: It might be difficult to determine whether the alleviated rosacea-like symptoms in Lrrc4 mutant mice are due to VIP inhibition or whether it is the combined PAC1/VPAC subtype receptor inhibition to play a role in improving symptoms, considering that VIP and PACAP both bind with high affinity to VPAC1, VPAC2 and PAC1 receptors, with the only difference that PACAP exhibits about 1000-fold higher affinity for PAC1 than VIP55,56, and VIPhyb has also been reported to suppress peptide histidine isoleucine (PHI) and PACAP in addition to VIP57,58.