To determine whether plasma matrix metalloproteinase 9 (MMP-9) and MMP9 (-1562C-->T) polymorphism have an effect on the disease phenotype in primary Sjogren's syndrome (pSS).
Plasma MMP-9 concentrations and polymorphism of the MMP9 gene were analysed in 66 patients with pSS. These data were studied in relation to the clinical data of the patients. The genetic data of patients were compared with the data of 66 healthy subjects.
Plasma MMP-9 was higher in patients with definite pSS than in patients with possible pSS. This association was principally caused by higher plasma MMP-9 in patients with a positive Schirmer test and keratoconjunctivitis sicca. pSS patients with purpura, SS-A autoantibodies and RF had significantly lower plasma MMP-9 than patients without these characteristics. The overall MMP9 (-1562C-->T) allele frequencies were similar in patients and control subjects. The frequency of the allele T was higher in patients without Raynaud's phenomenon than in the control group.
MMP9 (-1562C-->T) could not be used for risk assessment in pSS. The presence of the rarer allele T may decrease the risk of Raynaud's phenomenon in pSS. High plasma MMP-9 is indicative of definite pSS but may paradoxically have a preventive effect on the eruption of purpura and on the development of autoantibody reaction in pSS.