Hypocomplementemia in Primary Sjogren's Syndrome: A Retrospective Study of 120 Treatment-Naive Chinese Patients.

objectiveTo determine the prevalence of hypocomplementemia in primary Sjogren's syndrome (pSS) patients and compare the clinical characteristics of patients with and without hypocomplementemia.

methodsA retrospective study was conducted in 120 treatment-naive Chinese patients that met the 2012 American College of Rheumatology Classification Criteria for pSS and were followed up for 3 to 24 months. Based on the complement results, patients were divided into four groups: only low C3, only low C4, both low C3 and C4 (double low), normal group. The data on patient demographics, clinical manifestations, laboratory results, disease activity and pharmacologic therapy were collected and compared among the four groups.

resultsThe prevalence of only low C3, only low C4, both low C3 and C4 in pSS patients was 21.7%, 16.7%, and 10%, respectively. The mean age of the four groups was significantly different. Unlike rampant caries and parotitis, the prevalence of dry eyes and dry mouth differed among the four groups. The proportion of patients with anemia, leukocytopenia, lymphadenopathy, hematological involvement and fatigue was significantly higher in the double low group and lower in the normal complement group. The proportion of patients with increased serum IgG was higher in the only low C4 group than in the other groups. Logistic regression revealed that hypocomplementemia was an independent risk factor for lymphadenopathy and leukopenia. The double low group had a significant history of exposure to glucocorticoids and cyclophosphamide, compared with other groups.

conclusionOur study found that the clinical characteristics of pSS patients with hypocomplementemia differed from those without hypocomplementemia. Hypocomplementemia in pSS was associated with hematological involvement, hyper-IgG, lymphadenopathy, and fatigue, contributing to more significant exposure to glucocorticoid and cyclophosphamide.