Primary Sjögren’s syndrome (SS) is a chronic autoimmune disease that affects primarily the salivary and lacrimal glands. Nitric oxide (NO) has been implicated in the pathogenesis of SS and raised nitrite concentrations have been observed in the saliva of patients with SS.1 NO is a molecule that plays a key role in many physiological and pathological processes. It is produced in vivo from the aminoacid l-arginine by a family of nitric oxide synthases (NOS), of which three isoforms have been identified, i.e. neuronal, endothelial and inducible.2 Endothelial nitric oxide synthase (eNOS) is a constitutively expressed isoform of NOS. The eNOS gene entails several polymorphisms, of which for …