Factors associated with secondary immune thrombocytopenia in patients with primary Sjögren's syndrome: a retrospective study of 639 cases.

OBJECTIVES: To investigate the clinical characteristics and relevant factors of secondary immune thrombocytopenia (ITP) in patients with primary Sjögren's syndrome (pSS). METHODS: Patients with pSS being treated between 2013 and 2020 in China-Japan Friendship Hospital were retrospectively analysed. Clinical characteristics were compared between pSS patients with and without secondary ITP. Logistic regression analysis was performed to identify factors associated with secondary ITP in patients with pSS. RESULTS: 639 patients with pSS were included in this study, among which 566 (88.6%) were women. The prevalence of secondary ITP in patients with pSS were 12.4%. Among pSS patients with secondary ITP, 55.7% had mucocutaneous bleeding and 8.9% experienced visceral bleeding. Lymphopenia (OR=3.154, 95% CI 1.185-8.395, p=0.021), anaemia (OR=2.416, 95% CI 1.250-4.668, p=0.009), low C4 (OR=2.904, 95% CI 1.563-5.394, p=0.001), and positive anti-RNP (OR=2.777, 95% CI 1.070-7.202, p=0.036) were significantly related to secondary ITP, while interstitial lung disease (ILD, OR=0.429, 95% CI 0.203-0.907, p=0.027), ANA ≥1:320 (OR=0.469, 95% CI 0.221-0.996, p=0.049) and positive anti-SSB (OR=0.288, 95% CI 0.126-0.685, p=0.003) were negatively associated with secondary ITP in patients with pSS. CONCLUSIONS: Over 10% of patients with pSS had secondary ITP, among whom visceral bleeding was comparatively rare. Lymphopenia and anaemia were positively related to secondary ITP, while ILD was negatively associated with secondary ITP. Low C4 and positive anti-RNP seem to be two potential risk factors for secondary ITP in patients with pSS, while ANA ≥1:320 and positive anti-SSB may be two potential protective factors.