Unmasking Renal Disease in Systemic Lupus Erythematosus: Beyond Lupus Nephritis.

A 64-year-old Caucasian woman with a history of hypertension and systemic lupus erythematosus (SLE) was referred to a nephrology clinic due to persistent microscopic hematuria and trace proteinuria. Initial tests showed elevated antinuclear antibodies (ANA), anti-double-stranded DNA (anti-dsDNA), and anti-Sjögren's syndrome-related antigen A (anti-SSA) levels, while other markers remained within normal limits. Over the course of a year, her urine protein-creatinine ratio increased, prompting a renal biopsy. The biopsy revealed focal crescent formation in some glomeruli and mild segmental mesangial hypercellularity in others. Although the possibility of antineutrophilic cytoplasmic antibody (ANCA)-associated nephritis with superimposed IgA nephropathy was considered, negative myeloperoxidase and proteinase 3 antibody tests led to a final diagnosis of IgA nephropathy. The patient's treatment included adding prednisone to her existing valsartan prescription for hypertension, which resulted in improved proteinuria. SLE is an autoimmune disease that can cause chronic inflammation and damage to vital organs. Approximately 50% of SLE patients may experience lupus nephritis (LN), underscoring the importance of urinalysis and renal function tests. This case presents a female patient with SLE and IgA nephropathy, a rare association that requires distinction as it affects disease management. IgA nephropathy is the most common cause of idiopathic glomerulonephritis and can lead to end-stage kidney disease in around 40% of cases. A renal biopsy is also crucial for diagnosing IgA nephropathy in patients with or without another autoimmune disease. Focal crescent formation, a histological feature observed in this case, helped exclude several diagnoses, such as lupus nephritis or pauci-immune glomerulonephritis. The primary goal of treating IgA nephropathy is to prevent disease progression. Initial treatment includes controlling blood pressure, reducing proteinuria, and implementing lifestyle modifications. Corticosteroid therapy may be considered if supportive care is insufficient.