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ANCA-negative paucine vasculitis occurs in 10% of patients with clinical characteristics with vasculitis associated with antibodies to the cytoplasm of neutrophils with a negative result. This presentation develops a restricted autoantibody response against a linear MPO epitope (present in 50% of patients with MPO-ANCA vasculitis). Result from masking of the epitope by a fragment of ceruloplasmin or the presence of anti-endothelial cell antibodies. Patients with negative antibodies usually present with renal disease limited to the kidney or mild systemic disease, however the clinical course and response to treatment differs from patients with a positive test.
29-year-old female systemic lupus erythematosus diagnosed in 2019 due to hematological and mucocutaneous involvement, immunological tests were performed with positive antinuclear antibodies, receiving treatment for 1 year with azathioprine, prednisone and maintenance with hydroxychloroquine. Her condition began in October 2021 with renal manifestations presenting proteinuria 672 mg and active sediment, instituting treatment based on mycophenolic acid and tacrolimus, maintaining treatment for 9 months. However, in July 2022, joint activity was presented in laboratory studies with creatinine 1.03 mg/dl, anti double-stranded DNA 217 IU/ml, anti nuclear ribonucleoprotein 2.71. IU/ml, PR3 Antibodies 3.3 UR/ml and MPO 2.6 UR/ml, complement C3 127 mg/dl and C4 25.3 mg/dl with urine protein 703 mg/dl with urine albumin 457 mg/24 hrs. A biopsy was performed in December 2022, which reported 19 glomeruli, 3 of which were sclerosed globally. In 4 with active extracapillary hypercellularity, presence of cellular crescents with active extracapillary lesion and in 1 with fibrocellular crescents. Prominent and vacuolated podocytes, the interstitium has few patches of fibrosis with associated tubular atrophy that affects an approximate cortical surface of 10%, immunofluorescence with positive IGG with a granular pattern in the mesangium and very focal in the glomerular basement membranes, C3C positive with a granular pattern in the mesangium determining by pathology study active and chronic extracapillary proliferative glomerulonephritis with few deposits of immune complexes (pauciimmune). It was decided to start remission induction treatment with cyclophosphamide. In February 2023, a negative anti-ANCA PR3 and MPO vasculitis profile was reported, with albumin in 24-hour urine of 464 mg. Protein in 24-hour urine 752.25 mg. In March 2023 he presented with creatinine 0.80 mg/dl, urine protein 338 mg in 24 hours and albuminuria 268 mg/24 hrs with creatine clearance 96.25 ml/min. Continuing maintenance management with azathioprine and prednisone. It integrates a clinical syndrome of proteinuria, hematuria, without deterioration of renal function, eucomplementemic that, together with the findings by histopathological study, presenting cellular and fibrocellular crescents with pauciimmunity in immunofluorescence, an autoimmune phenomenon such as ANCA negative vasculitis is suspected.
Pauciimmune glomerulonephritis is characterized by the presence of cellular crescents or fibrinoid necrosis in a renal biopsy specimen, in the absence of significant immune deposits on immunofluorescence study (0 or 1+ IgG or C3 staining). In the literature, cases with negative haunches are reported in which a different clinical spectrum is present than those with positive disease, with fewer constitutional and extrarenal symptoms. In the previously mentioned case, the patient has a history of systemic lupus erythematosus that presents deterioration in renal function with evidence of subnephrotic proteinuria and glomerular hematuria.
The renal biopsy was essential to guide the management when presenting extracapillary proliferative glomerulonephritis with few deposits of immune complexes, having a favorable response to its management. However, in reviews, the treatment remains uncertain. Patients with ANCA-negative immune pauci glomerulonephritis had worse renal outcomes than their ANCA-positive counterparts when considered a different pathological entity.