Systemic Lupus Erythematosus With IgA Nephropathy: Challenges in Diagnosis and Management.

BACKGROUND Systemic lupus erythematosus (SLE) commonly involves the kidneys, most often as lupus nephritis (LN), which affects up to 60% of patients who have SLE, and is a major cause of morbidity. IgA nephropathy (IgAN), the most common primary glomerulonephritis, follows a benign course but rarely coexists with SLE. This overlap creates a significant diagnostic dilemma because both conditions present with proteinuria, hematuria, and impaired kidney function. Whether this demonstrates a causal link or a simple coincidence remains debated. CASE REPORT We present the case of a young woman with diagnosed SLE, previously complicated by seizures, who presented with nephrotic-range proteinuria, edema, and hematuria, mimicking a LN flare. She met the EULAR/ACR criteria for SLE exclusive of renal involvement. However, renal biopsy revealed dominant mesangial IgA deposition without IgG or C1q, with an Oxford MEST-C score of M1E0S1T0C0, confirming IgAN. Early immunosuppression was administered, owing to the severity of the presentation. This resulted in marked improvement, with proteinuria decreasing significantly and stabilization of renal function on follow-up. CONCLUSIONS This case illustrates that severe IgAN can occur in patients with SLE and be clinically indistinguishable from an LN flare. Careful histopathological assessment, particularly immunofluorescence, is important to differentiate IgAN from classic LN, as management may differ. The aggressive presentation and favorable response to immunosuppression suggest that active SLE can exacerbate underlying IgAN. This co-occurrence raises questions about whether IgA-dominant nephritis in SLE is an incidental finding or is a linked pathogenesis.