Abstract: FR-PO982
Discovering the Etiology of a Rare Diagnosis of Anti-brush Border Antibody (ABBA) Disease
Session Information
- Pathology and Lab Medicine - 1
October 25, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pathology and Lab Medicine
- 1800 Pathology and Lab Medicine
Authors
- Contreras, Jessenia Ariana, Kaiser Permanente Northern California Region, San Francisco, California, United States
- Iwasaki, Sumie, Kaiser Permanente Northern California Region, San Francisco, California, United States
Introduction
Anti-low density lipoprotein receptor related protein 2 (Anti-LRP2) nephropathy (a.k.a. anti-brush border antibody (ABBA) disease) is a rare entity with only around 67 cases confirmed by LRP2 immunostaining and indirect immunofluorescence. It is common in white men around the age of 70s, and there is often an association with autoimmune diseases, paraneoplastic syndromes, or monoclonal gammopathy. LRP2 is found in multiple organs, but within the kidneys, LRP2 is expressed only in proximal tubular (PT) brush borders. The disease causes acute tubular injury (ATI) via immunoglobulin G (IgG) immune complex deposits along the PT basement membrane and circulating autoantibodies to the PT brush border protein LRP2. We report a case of ABBA and the process of evaluating the etiology.
Case Description
A 74-year-old man with history of dextrocardia s/p heart transplant, osteopenia, and CKD stage IV presented with back pain and weakness, with hypercalcemia [13 mg/dL], anemia, and acute on CKD. PET scan was negative. Calcium supplements were discontinued on admission, and he was treated with IV fluids with some improvement in hypercalcemia but not in renal function. Hypercalcemia workup revealed suppressed PTH, elevated vitamin D 25- OH and ACE levels, small M-protein spike on SPEP and IgG kappa on serum immunofixation; PTHrP, Vitamin D 1,25- OH2, TSH, ANCA, ANA panel, and kappa/lambda light chain ratio were normal. He had a recent history of Epstein- Bar Viremia but no signs of PTLD. Imagings were unremarkable. Renal biopsy showed ATI with tubular membrane disease deposits consistent with ABBA. Confirmatory testing for anti-LRP2 was sent to Arkana. The patient had worsening renal function and started on dialysis.
Discussion
This rare case of ABBA assesses potential etiologies. There could be an association between ABBA and heart transplant but there were no indications to check DSAs. Regarding his hypercalcemia, LRP2 is also located in the parathyroid gland, and unclear whether the autoantibodies affected the calcium sensing receptor. We are continuing to rule out other possibilities prior to initiating treatment, but most patients with ABBA do not respond to immunosuppressants and have poor prognosis.