• Ling Li, Zhi Yang, Tian Tao, Mei Yang, and Zhang-Xue Hu.
• Renal Division, Department of Medicine.
• Medicine (Baltimore). 2021 Mar 5; 100 (9): e24887e24887.

RationaleMembranous glomerulonephritis (MN) is the leading cause of nephrotic syndrome in adults and is classified as primary or secondary. Secondary MN accounts for 20% to 30% of all MN cases and can arise from a number of conditions, including autoimmune diseases. Recently exostosin 1/exostosin 2 (EXT1/EXT2) have been identified as the common antigens in secondary autoimmune MN and are present in cases of pure membranous lupus nephritis (LN). The treatment of EXT1/EXT2-associated MN remains elusive.Patient ConcernsWe present the case of a 15-year-old female who presented with nephrotic syndrome, positive ANA and dsDNA, and low serum complements. A renal biopsy revealed pure membranous nephritis with IgG and C3 deposition. EXT1 was found along the glomerular capillary walls and stained positive, while phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) were negative.DiagnosisThe patient was diagnosed with ETX1-associated membranous LN.InterventionsShe was treated with prednisone and multiple low-dose rituximab (4 200 mg doses, approximately every 2 months, based on CD19+ cells counts).OutcomesThe patient had complete remission within 8 months later, and she remained in remission for the 16-month period of follow-up.LessonsTo our knowledge, this is the first case of EXT1-associated MN that has been successfully treated by multiple low-dose rituximab. Further studies can investigate the optimal dosage and treatment protocol.Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.

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