Complement Component 4D (C4d) Staining in Lupus Nephritis: Correlating Renal Histopathological Features With Clinical...

Introduction Systemic lupus erythematosus frequently manifests as lupus nephritis (LN), a major cause of renal morbidity. Standard markers lack specificity, making renal biopsy essential. Complement component 4D (C4d) staining, reflecting classical complement activation, correlates with histopathological lesions and outcomes. This study evaluates C4d's clinical relevance in biopsy-proven LN, emphasizing its potential in detecting disease severity. Materials & methods This observational study at Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, conducted from September 2021 to August 2022, enrolled 45 adults with biopsy-proven LN; 43 completed follow-up. Participants were selected based on revised American College of Rheumatology (ACR) criteria and underwent thorough clinical evaluation, serological testing, and ultrasound-guided renal biopsy. Histopathological assessment followed the International Society of Nephrology and the Renal Pathology Society (ISN/RPS) 2003 classification, including activity and chronicity indices and immunohistochemical C4d staining. Follow-up investigations were performed at two and six months. Results Among the 43 patients with LN (mean age 28.4 ± 7.7 years; 86% female subjects), 42 (97.7%) patients had hematuria and 25 (58.1%) had renal impairment. Class IV was the predominant histological subtype in 18 (41.9%) cases, with mild chronicity in 20 (71.4%) cases. C4d deposition, primarily arteriolar in 24 (55.8%) cases, correlated significantly with Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores and histological activity indices (p<0.05). There is a significant relationship between C4d intensity and SLEDAI score, highlighting the prognostic utility of C4d staining. Conclusion The present study identifies C4d staining to be associated with active renal damage and higher SLEDAI scores, reflecting immune-mediated injury. These findings highlight its value as a potential marker that may enhance current histological assessment. Therefore, staining with C4d on renal biopsy may be emphasized for early detection of severity in patients with lupus.