Prognostic factors for the development of systemic lupus erythematosus in patients with immune thrombocytopenia

BACKGROUND: Patients with immune thrombocytopenia (ITP) have a risk of developing systemic lupus erythematosus (SLE). We sought to examine the clinical characteristics of patients with primary ITP who later developed SLE and identified the risk factors for the development of SLE. METHODS: We retrospectively examined patients who were diagnosed with primary ITP at a tertiary hospital between August 2001 and November 2019. We compared the clinical characteristics according to the development of SLE. Logistic regression analysis was performed to identify the factors associated with the development of SLE. RESULTS: Of 130 patients with primary ITP, 10 (7.7%) were later diagnosed with SLE during follow-up (median, 30 months [IQR, 15.5–105]). The presence of skin bleeding, organ bleeding, lymphocytopenia, anemia, and antinuclear antibody (ANA) positivity (≥ 1:160) were more common among patients who later developed SLE than did those who did not develop SLE. Multivariate analysis showed that young age (< 40 years; odds ratio [OR], 6.307 [95% confidence interval (CI), 1.114–34.908]; P = 0.035), organ bleeding (OR, 13.672 [95% CI, 2.437–76.689]; P = 0.003), and ANA positivity (1:160; OR, 6.638 [95% CI, 1.399–31.504]; P = 0.017) were significantly associated with the development of SLE. CONCLUSIONS: Young age (< 40 years), organ bleeding, and ANA positivity (≥ 1:160) were risk factors for the development of SLE in patients with primary ITP. Close follow-up is needed to detect the development of SLE in patients with ITP and the abovementioned risk factors.