Background Systemic lupus erythematosus (SLE) is a chronic condition with a broad clinical spectrum, which can affect multiple organs and systems. Although the most featuristic autoantibodies are anti-DNA and anti-Sm antibodies, anti-SS-A antibody and anti-SS-B antibody are detected in 30–40% and 7–45% of SLE patients, respectively. However, the clinical features of those positive patients are unclear.
Objectives The aim of this study was to clarify the associations of anti-SS-A and anti-SS-B antibodies with the clinical features of SLE and histological findings of lupus nephritis (LN).
Methods We enrolled consecutive Japanese patients with SLE who had visited Keio University Hospital from 2013 to 2015 and whose anti-SSA and anti-SSB antibodies were measured. The patients were divided according to the presence or absence of anti-SS-A and anti-SS-B antibodies, and their associations of the clinical features and renal biopsy histological findings were examined.
Results A total of 253 patients were enrolled, 215 (84%) were female, and the mean age was 55.2 years. Anti-SS-A antibody was detected in 152 cases (69%), and anti-SS-B antibody in 40 cases (18%). No difference was found in sex, age, the rates of anti-DNA and anti-Sm positivity between both the anti-SS-A positive group and the anti-SS-A negative group, and between the anti-SS-B positive group and the anti-SS-B negative group. While the frequencies of oral ulcers (38% vs. 37%, p=0.83), arthritis (82% vs. 79%, p=0.58), serositis (23% vs. 22%, p=0.94), neuropsychiatric involvement (14% vs. 10%, p=0.35), LN (51% vs. 63%, p=0.07), leukopenia (74% vs. 69%, p=0.44), and thrombocytopenia (26% vs. 31%, p=0.44) were not different between the anti-SS-A positive group and the anti-SS-A negative group,.mucocutaneous involvement (84% vs. 63%, p=0.002), alopecia (37% vs. 19%, p=0.002), lymphopenia (97% vs. 89%, p=0.020) were significantly higher in the anti-SS-A positive group than the anti-SS-A negative group. The frequencies of neuropsychiatric involvement (24% vs. 10%, p=0.015) was significantly higher in the anti-SS-B positive group than the anti-SS-B negative group. The period from the SLE onset to the LN onset was significantly shorter in the anti-SS-A positive group than the anti-SS-A negative group (4.0 years vs. 9.0 years, p=0.005), and in the anti-SS-B positive group than the anti-SS-B negative group (0.4 years vs. 6.8 years, p=0.008). Focusing on the histological findings of LN patients, the anti-SS-A positive group had significantly lower rate of renal tubular atrophy (8.0% vs. 16%, p=0.042) and interstitial fibrosis (7.6% vs. 16%, p=0.031) than the anti-SS-A negative group. The anti-SS-B positive group had also significantly lower rate of renal tubular atrophy (3.3% vs. 13%, p=0.048) and interstitial fibrosis (2.1% vs. 13%, p=0.016). Finally, chronicity Index was significantly lower in the anti-SS-A positive group (2.37 vs. 4.14, p=0.002) and in the anti-SS-B positive group (1.17 vs. 3.33, p=0.008).
Conclusions SLE patients positive for anti-SS-A and anti-SS-B antibodies had characteristics with frequent mucocutaneous involvement, alopecia, neuropsychiatric involvement, and lymphopenia. They should be followed carefully for early onset of LN.
Disclosure of Interest None declared