ANCA-NEGATIVE PAUCI-IMMUNE GLOMERULONEPHRITIS AS A PARANEOPLASTIC MANIFESTATION OF SARCOMATOID MALIGNANCY

Background: Pauci-immune glomerulonephritis (PIGN) is a type of small vessel vasculitis associated with anti-neutrophilic cytoplasmic antibodies (ANCA). However, about 10-20% of PIGN patients have negative ANCA serologies. PIGN as a paraneoplastic syndrome is rarely described in literature with a few cases reporting an association with lung cancer. Objectives: We describe a case of ANCA negative glomerulonephritis in a patient with underlying malignant sarcoma responsive to rituximab. Methods: An 80-year-old female was admitted with complaints of upper abdominal pain and new onset hematuria for 2 days. Vital signs were stable, and physical exam was remarkable for mild tenderness on deep epigastric palpation. Initial laboratory workup was significant for acute kidney injury with serum creatinine of 2.1 mg/dl (creatinine two months ago at outpatient visit was 1.0 mg/dl). Urinalysis showed 4+ proteinuria and dysmorphic red blood cells. CT scan of the abdomen revealed a soft tissue mass surrounding celiac artery and a right adrenal hypodense mass. Further serologies to elucidate the cause of kidney injury revealed normal perinuclear-ANCA and cytoplasmic-ANCA levels. Renal biopsy was positive for focal segmental necrotizing and crescentic glomerulonephritis consistent with pauci-immune vasculitis. She also underwent right adrenal and celiac mass biopsy; both revealing malignant spindle and epithelioid cell neoplasm consistent with undifferentiated pleomorphic sarcoma (UPS). Our patient was treated with four rounds of plasmapheresis followed by 600mg rituximab infusion which decreased her creatinine to 1.7 mg/dl and resolved hematuria within 10 days of admission. She was followed up in rheumatology clinic two weeks later where she denied further hematuria and was given another round of 600mg rituximab infusion. Results: UPS is a rare soft tissue cancer with a 5-year survival rate as low as 15% in metastatic disease. Paraneoplastic manifestations of UPS are seldom described in literature due to poor prognosis of the disease and low annual incidence. PIGN is scarcely reported in association with lung carcinoma in a few case reports[1, 2]. It is interesting to note that in these cases there was antecedent chemotherapy raising suspicion of vasculitis induced by adjuvant agents. As our patient did not receive chemotherapy, PIGN was deemed to be a paraneoplastic phenomenon secondary to malignant sarcoma. Conclusion: This case underscores the importance of recognizing sarcoma as a possible etiology of paraneoplastic ANCA-negative PIGN. We also explain how plasmapheresis and rituximab may play a role in the treatment of renal dysfunction in these patients. REFERENCES: [1]Kancharla P, Surapaneni BK, Goldfinger M, Hennrick K, Ozeri DJ. Paraneoplastic Seronegative Pauci-Immune Glomerulonephritis Associated with Lung Adenocarcinoma Responds to Rituximab: A Case Report. Case Rep Oncol. 2018;11(2):372-7. [2]Morikawa T, Yoshida A, Kobayashi S, Shibata M, Hamada M, Kishida M, et al. AP-VAS 2012 case report: a case of ANCA-negative pauci-immune crescentic glomerulonephritis associated with IL-6-producing adenosquamous cell carcinoma of the lung. CEN Case Rep. 2013;2(2):158-64. Disclosure of Interests: None declared Citation: , volume 81, supplement 1, year 2022, page 1860Session: Educational cases (Publication Only)