Sjögren’s syndrome is characterized by immune system activation that leads to the over production of cells called autoantibodies which attack the tissues and glands in the body. More specifically, anti-SSA and anti-SSB autoantibodies are more active in individuals living with rheumatic conditions. In the case of Sjögren’s syndrome, moisture-producing glands, such as those that produce tears and saliva, are the primary targets of this misdirected autoimmune attack by anti-SSA and anti-SSB autoantibodies. Anti-SSA and anti-SSB autoantibodies are usually detected in about 50% to 70% of Sjögren’s patients depending on the study. Their presence is associated with earlier onset and higher prevalence of additional symptoms beyond dry eye and dry mouth. However, our understanding of the 30-50% Sjögren’s patients who test negative for anti-SSA and anti-SSB autoantibodies is limited.
A study titled “Anti-SSA/SSB-negative primary Sjögren’s syndrome showing different clinical phenotypes: a retrospective study of 934 cases” was published in the journal Advances in Rheumatology in 2023. A group of researchers examined the medical records of 934 adults with Primary Sjögren’s syndrome (patients with Sjögren’s without another associated autoimmune disease) who were being followed at China-Japan Friendship Hospital between January 2013 and March 2022. Most of the patients were female, and the average age of the sample was 58.
Further analysis of medical records found that 68% (635) of patients tested positive for one or both anti-SSA and anti-SSB autoantibodies, while the remaining 32% (299) patients tested negative for both autoantibodies. Among those who tested positive for these common autoantibodies, 218 underwent a salivary gland biopsy and 194 (98%) showed signs of immune cell attack. On the other hand, all the patient who tested negative for autoantibodies underwent a minor salivary gland biopsy and showed signs of immune cell attack.
Here are some of the interesting results:
- Patients who tested negative for the two common autoantibodies were significantly older (mean age of 61.7 vs. 54.8) and had shorter disease duration (mean of 24 vs. 48 months) when compared to those who tested positive.
- The proportion of males was significantly higher in the autoantibody-negative group (24.7% vs. 9.4%).
- Interstitial lung disease (ILD), a group of conditions marked by inflammation and scarring of lung tissue, were more prevalent in patients who tested negative for anti-SSA and anti-SSB autoantibodies than in patients testing positive (71.2% vs. 40.8%).
- A low platelet count or thrombocytopenia, however, was less frequently seen in the autoantibody-negative group when compared to the positive group (6.7% vs. 13.6%).
In summary, a multivariate statistical analysis showed that being older, having a shorter disease duration, being male and having an ILD are associated with a significantly higher chance of testing negative for anti-SSA and anti-SSB autoantibodies. The researchers concluded that individuals who test negative for common antibodies have “distinct clinical phenotypes [presentations]” when compared to those with positive antibodies.
