Serum level of galectin-9 in systemic lupus erythematosus patients with lupus nephritis: Relation to clinical characteristics and disease activity

Aim of the work: To assess galectin-9 (Gal-9) level in the serum of systemic lupus erythematosus (SLE) patients with and without renal involvement and clarify its relation with disease activity.Patients and methods: 50 SLE patients; 25 with lupus nephritis (LN) and 25 without as well as 25 controls were studied. Systemic Lupus International Collaborating Clinics (SLICC) renal activity score and SLE disease activity index 2000 (SLEDAI-2 K) were determined. Serum Gal-9 was measured in all participants. Results: Gal-9 level was significantly elevated in SLE patients with (16.7; 11.6-33.7 ng/ml) and without (15.9; 11.8-25 ng/ml) compared to controls (3.9; 2.8-5.4 ng/ml) (p < 0.001) but was comparable between the patients groups (p = 0.83). In LN patients, serum Gal-9 and SLICC renal activity score significantly correlated (r = 0.48, p = 0.016). Serum Gal-9 significantly correlated with SLEDAI-2 K in patients with (r = 0.71, p < 0.001) and without (r = 0.95, p < 0.001) LN, with anti-double stranded deoxyribonucleic acid (anti-ds-DNA) titers (with r = 0.57, p < 0.001 and without r = 0.79, p < 0.001) and inversely with C3 (with r = -0.44, p = 0.027 and without r = -0.63, p < 0.001) and C4 (with r = -0.47, p = 0.018 and without r = -0.43, p = 0.03). Gal-9 had an area under the curve (AUC) of 0.96 to distinguish SLE cases from control. However, AUC between LN group and nonnephritic SLE was 0.48. On regression, SLEDAI-2 K was the only significant factor associated with serum Gal9 (p < 0.001).Conclusion: In SLE patients, significantly raised Gal-9 levels and relation with disease activity were detected indicating its clinical relevance as biomarker of disease activity and its potential value in the disease diagnosis. Its value in discriminating LN from non-nephritic SLE is limited.