Eicosanoid receptors mRNA pattern observed in our patient's groups suggest that down-regulation of EP1 and EP3 in the nasal polyp tissue and up-regulation EP2 and EP4 in both chronic rhinosinusitis groups may play a role in the development of the diseases and their regulation do not directly depend of eosinophil activation. The gene discussed is PTGER4; the disease is chronic rhinosinusitis.