Interstitial lung disease, tear issues can mark primary Sjögren’s with rarer autoantibodies

Study into patients negative for anti-SSA and anti-SSB autoantibodies

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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Almost one-third of patients with primary Sjögren’s syndrome (pSS) tested negative for the disease’s two most common autoantibodies — anti-SSA and anti-SSB autoantibodies — in a retrospective study conducted in China.

Interstitial lung disease (ILD), a group of conditions marked by inflammation and scarring of lung tissue, and poorer tear production were more prevalent in these people than in pSS patients positive for these common autoantibodies.

Findings suggest that “pSS patients testing negative for anti-SSA and anti-SSB have distinct clinical phenotypes [presentations] to those with positive antibodies,” the researchers wrote.

The study, “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.

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Most with primary Sjögren’s syndrome positive for 2 common autoantibodies

B-cells are a type of immune cell responsible for the production of antibodies — proteins that can help protect the body against infections caused by bacteria and viruses.

Primary Sjögren’s syndrome is characterized by B-cell abnormalities that lead to the production of self-targeting antibodies, called autoantibodies, particularly anti-SSA and anti-SSB autoantibodies. Moisture-producing glands, such as those producing tears and saliva, are the primary targets of this misdirected autoimmune attack, but other tissues also can be affected.

Anti-SSA and anti-SSB autoantibodies are usually detected in about 50% to 70% of pSS patients. Their presence is associated with early disease onset and a higher prevalence of disease symptoms beyond those involving saliva or tear-producing glands.

However, the clinical features of pSS patients who test negative for anti-SSA and anti-SSB autoantibodies remain poorly understood, the researchers noted.

Scientists in Beijing retrospectively analyzed medical records covering 934 adults with pSS being followed at China-Japan Friendship Hospital between January 2013 and March 2022. Most of the patients — 800 — were women, and the group had an average age of 58.

A third of these patients (32%) tested negative for both anti-SSA and anti-SSB autoantibodies, while the remaining 68% were positive for one or both autoantibodies.

Among those positive for these common autoantibodies, 218 underwent a minor salivary gland biopsy, with 194 (97.7%) showing signs of immune cell infiltration in agreement with pSS.

All of the 299 antiautobody-negative patients also showed these hallmark pSS signs in a minor salivary gland biopsy.

pSS patients who tested negative for anti-SSA and anti-SSB autoantibodies were significantly older (mean age of 61.7 vs. 54.8) and had shorter disease duration (mean of 24 vs. 48 months) than those who tested positive for those autoantibodies. The proportion of females also was significantly lower in the autoantibody-negative group (75.3% vs. 90.6%).

ILDs were significantly more prevalent in pSS patients who tested negative for anti-SSA and anti-SSB autoantibodies than in patients testing positive (59.2% vs. 28.8%). A low platelet count or thrombocytopenia, however, was less frequently seen in the autoantibody-negative group (6.7% vs. 13.6%). These two findings “are particularly meaningful from the clinical perspective,” the researchers wrote.

Problems with tear production, as assessed by the Schirmer test, also were more prevalent in autoantibody-negative patients relative to the others (96% vs. 89.1%).

A multivariate statistical analysis showed that being male, having an ILD, an abnormal Schirmer test result, and testing positive for an autoantibody called anti-CENP-B all associated with a significantly higher chance of testing negative for anti-SSA and anti-SSB autoantibodies.

Study findings in these Chinese patients suggest that “pSS patients with anti-SSA and anti-SSB antibody negativity have distinct clinical manifestations compared to those testing positive for these antibodies, [implying] the underlying pathological [disease-causing] mechanisms may somewhat different,” the researchers wrote.

“More high-quality prospective studies are needed to confirm these findings,” they added, as well as research into the likely “mechanisms underlying the increased prevalence of ILD in pSS patients with anti-SSA and anti-SSB antibody negativity,” which still “remain unclear.”