Background: Lupus nephritis (LN) is a common and serious complication in systemic lupus erythematosus (SLE) and
is associated with significant mortality and morbidity of SLE patients. The conventional laboratory markers used in clinical
practice such as serum complement levels and double-stranded DNA antibodies are unreliable indicators of LN as they lack
both sensitivity and specificity for prediction of active or relapsing LN. Studies have shown that podocyte injury occurs in the early stages of glomerular damage in LN, and that quantification of podocyturia could be used as a marker for active disease. Podocalyxin (PCX) is probably the most frequently used marker protein for podocyturia. Aim of the work: To investigate urinary podocalyxin (u-PCX) as a marker of lupus nephritis (LN) disease activity. Methods: 63 patients with clinical and biopsy proven LN were recruited and divided into two groups; 35(55.56%) patients with active LN & 28(44.44%) patients with inactive LN. Estimation of u-PCX/creatinine ratio, urine protein /creatinine ratio (PCR), erythrocyte sedimentation rate, C reactive protein, serum albumin, serum complement C3 and C4, anti-double stranded DNA antibody titers, serum creatinine, estimated glomerular filtration rate and renal biopsy were done. Results: Patients with active LN had significant higher levels of PCR (1159.38±724.37 Vs 332.29±145.10), u-PCX (109.18±28.21 Vs 67.93±8.24), and SLEDAI-2K renal score (6.83±2.16 Vs 2.0±1.17) (P<0.001). However, active LN group had significant lower serum albumin (2.87±0.51 Vs 3.61±0.22, P<0.001). In active LN; u-PCX correlated positively with PCR (r=0.516, p=0.002), SLEDAI-2k (renal) (r=0.568, p<0.001), ads DNA ab (r=0.362, p<0.032) and negatively with serum albumin (r= - 0.421, p=0.014).Moreover, SLEDAI-2k renal score was negatively correlated with serum albumin(r=-0.710, P<0.001). Conclusion: u-PCX could be served as a marker of LN disease activity. [Egypt J Rheumatology & Clinical Immunology, 2016; 4(1): 23-31]