Anti-LDL Receptor-Related Protein 2 (LRP2) Nephropathy

Introduction: Anti-LRP2 nephropathy is an uncommon kidney disease primarily affecting older individuals. It is marked by acute kidney injury (AKI) and progressive damage to renal tubules, characterized by IgG immune complex deposits along the basement membrane of proximal tubules. This case report highlights a patient presenting with acute kidney injury and subnephrotic proteinuria, in whom anti-LRP2 nephropathy was confirmed by renal biopsy. Case Description: A 75 year olf female with medical history of anemia, breast cancer, hypertension,presented with acute kidney injury and eosiniphilia as lab studies notable for elevated creatinine (1.51–1.56 mg/dL from baseline 1.2 mg/dL) and new-onset subnephrotic range proteinuria (urine protein-to-creatinine ratio: 2.42 mg/mg). She denied any systemic symptoms of fever, weight loss, nausea, vomiting, diarrhea, respiratory distress, hematuria, edema or weakness. She has undergone bilateral mastectomy and cholecystectomy and has no history of smoking, alcohol, or drug use. Immunological workup revealed positive ANA and anti-dsDNA, while other markers were negative. Complement levels were normal. Urinalysis showed 2+ blood, 4+ fine granular casts, and 100+ proteins. Kidney ultrasound showed small kidneys without hydronephrosis or calculi. Given the renal dysfunction and positive dsDNA, lupus nephritis was suspected. A kidney biopsy was performed for definitive diagnosis and returned back positive for anti LRP2 ab associated nephropathy. Discussion: Anti-LRP2 nephropathy is a rare kidney disorder seen in patients over 60, often linked to monoclonal gammopathies or malignancies. It causes tubular dysfunction and progressive renal failure, with proteinuria and electrolyte imbalances. Biopsy shows segmental membranous features and IgG staining along proximal tubules. Prognosis is poor, with progression to end-stage kidney disease. Treatment options include immunosuppressants, corticosteroids, and rituximab, but guidelines remain unclear. To our knowledge, this case represents a rare instance of ABBAD occurring alongside positive ANA and anti-dsDNA serology in an elderly patient. It underscores the importance of pathologists maintaining a high level of suspicion for ABBAD, as it can manifest independently or in conjunction with other autoimmune nephritides.