HP and systemic lupus erythematosus: Despite the fact that Caucasian SLE patients exhibited higher plasma zonulin levels compared to the control group (7.566 ± 1.368 ng/mL vs. 2.306 ± 0.286 ng/mL, p < 0.01, Mann–Whitney-U-test), plasma zonulin levels did not correlate with disease activity measured by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI).