A Rare Case of Seronegative Lupus Nephritis Presenting as Immune Complex Diffuse Glomerulonephritis

Introduction: SLE is a chronic autoimmune disease of unknown cause that can affect virtually any organ of the body. Immunologic abnormalities, especially the production of a number of antinuclear antibodies, are a prominent feature of the disease. Uncommonly, the diagnosis of SLE can still be made in the setting of a negative ANA based on a combination of consistent clinical signs and symptoms, laboratory testing, and biopsy results. Case Description: A 31-year-old male with a history of type 1 diabetes with diabetic retinopathy, and latent tuberculosis presented with progressive generalized edema, shortness of breath, and a diffuse rash over the course of 2-3 weeks. His initial clinical presentation, including renal dysfunction (creatinine 2.67 mg/dL, eGFR 38.1 mL/min), nephrotic-range proteinuria, hematuria, and hypoalbuminemia, raised concerns for nephrotic syndrome and nephritic syndrome. Differential diagnoses included diabetic nephropathy, immune complex-mediated glomerulonephritis, and heart failure. Autoimmune work up including ANA, anti-dsDNA, ANCA panel, rheumatoid factor, infectious work up and ASO were negative whereas complements were within normal limits and A1C was 7.7%. However, renal biopsy revealed immune complex-mediated diffuse proliferative glomerulonephritis with full-house staining, along with features of diabetic glomerulosclerosis, leading to a diagnosis seronegative lupus nephritis presenting as idiopathic immune complex glomerulonephritis. The patient was treated with pulse steroid therapy and mycophenolate mofetil, resulting in resolution of anasarca and partial improvement in renal function. Despite initial improvement, the patient was readmitted a month later with worsening scrotal edema, which was unresponsive to home diuretics. Management was adjusted with increased diuretics and an escalation of mycophenolate dosage as well. Discussion: This case underscores the diagnostic challenges in patients with multiple comorbidities, the importance of a multidisciplinary approach, and the complexity of managing glomerulonephritis in diabetic patients, highlighting the need for a thorough work-up including kidney biopsy to differentiate between autoimmune, infectious ,diabetic kidney disease , idiopathic MPGN and seronegative lupus nephritis which is very rare case.