Atypical Anti-Glomerular Basement Membrane Disease in a Patient with Systemic Lupus Erythematosus

Introduction: Atypical anti-GBM disease is characterized by unconventional clinical and histological features, specifically bright linear glomerular basement membrane(GBM) staining for immunoglobulins without the usual diffuse crescentic phenotype. This condition may be associated with other immunological disorders like SLE. Treatment strategies can range from addressing the underlying immunological issue to therapies similar to those for typical anti-GBM disease. Case Description: A 58-year-old female with a history of Type 2 Diabetes Mellitus, hypertension, and systemic lupus presented to the emergency department due to worsening shortness of breath and a dry cough. She exhibited acute hypoxic respiratory failure and acute kidney injury. Laboratory tests revealed protein and red blood cells in her urine, alongside dysmorphic red blood cells. Chest X-ray indicated bilateral alveolar opacities, and a bronchoscopy confirmed diffuse alveolar hemorrhage. Due to the severity of her condition, she required mechanical ventilation and renal replacement therapy. Serological tests confirmed a positive ANA with high titers, low complement levels (C3 and C4), and positive anti-dsDNA antibodies. However, anti-GBM antibodies, ANCA, serum electrophoresis, and other viral serologies were negative. A kidney biopsy showed focal global and segmental glomerulosclerosis consistent with nodular diabetic nephropathy and linear IgA deposition on the GBM, indicative of atypical anti-GBM disease, without necrosis or crescents present. The patient was treated for a lupus flare with pulse intravenous methylprednisolone followed by oral prednisone. She underwent seven sessions of plasma exchange and was started on intravenous cyclophosphamide. Ultimately, she was successfully weaned off mechanical ventilation and renal replacement therapy. Discussion: This atypical anti-GBM disease presented with IgA staining instead of IgG. The underlying lupus nephritis likely exposed GBM antigens, prompting this unique autoimmune response. Despite the kidney biopsy showing no evidence of lupus nephritis, the patient demonstrated active lupus flares clinically and serologically, including abnormal complements, ANA, and anti-dsDNA. Thus, treating the underlying lupus was deemed appropriate, with plasmapheresis added due to the pulmonary hemorrhage.