Decreased platelet serotonin levels (PSL) were measured in primary Sjogrens syndrome as well as in all examined inflammatory rheumatic disorders such as rheumatic arthritis (RA, systemic lupus erythematosus (SLE), systemic sclerosis (SSc), mixed connective tissue disorder (MCTD);in neuroimmunological disorders multiple sclerosis (MS) and depression.We measured PSL by using spectrofluorimetric method and two the most common serotonin transporter polymorphisms (SERTPR and SERTin2-VNTR) were determined by using PCR method.Magnitude ofplatelet serotonin depletion is determined and correlated with genetic findings, objective and subjective symptoms, neurological manifestations and laboratory parameters in patients with pSS and healthy controls.Different neuroimmunopatholoogical mechanisms are involved in the pathogenesis of autoimmune disorders whereas serotonin is responsible for various disorders and symptoms.