WHEN THE ANSWER IS IN THE URINARY SEDIMENT

Introduction:

Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease with significant morbidity and mortality, particularly when kidney involvement is present. The impact of ANCA positivity, along with serum anti-nuclear antibodies (ANA) and/or anti-double-stranded DNA (anti-dsDNA) antibodies, on the outcomes of AAV-associated glomerulonephritis (AAV-GN) is not well understood, though these markers are frequently observed. Some studies suggest that AAV-GN patients with positive ANA may experience more severe renal damage and worse chronic histopathologic findings.

Methods:

Results:

A 78-year-old man with a clinical history of controlled hypertension presented with a two-month history of fatigue, weakness, weight loss, afternoon fevers, night sweats, and myalgias. Despite multiple evaluations, including ruling out infectious and proliferative diseases like tuberculosis and cancer, a definitive diagnosis was not reached. Notably, the onset of his symptoms occurred two months after receiving his last COVID-19 vaccine. Upon admission, laboratory tests showed normocytic normochromic anaemia (Hb 10.5 g/dL), leucocytosis (17,300 cells/µL), an elevated erythrocyte sedimentation rate (99 mm/h), and normal renal function with a serum creatinine of 0.82 mg/dL. Haematuria and proteinuria were present from the onset of symptoms. Additional tests revealed positive ANCA-MPO (95 IU/mL), ANA (1:320), and anti-dsDNA (107 IU/mL), with normal complement levels. Physical examination was unremarkable except for a slim build and mild bimalleolar oedema. During hospitalization, the patient developed kidney dysfunction, with a peak serum creatinine of 2.78 mg/dL, a protein-to-creatinine ratio of 0.65 g/g, and 86 erythrocytes per high-power field (HPF). A diagnosis of AAV-GN was made, and immunosuppressive therapy was initiated with corticosteroids and rituximab. Kidney biopsy confirmed AAV-GN with crescents and fibrinoid necrosis, while immunofluorescence was negative, ruling out overlapping diseases. The patient showed partial remission following immunosuppressive induction. At a three-month follow-up, his serum creatinine was 1.36 mg/dL, urine analysis showed 7 erythrocytes/HPF, the protein-to-creatinine ratio was 0.21 g/g, and the ANCA-MPO titter had decreased to 45 IU/mL. At a six-month follow-up, his kidney function continued to improve with serum creatinine was 1,22 mg/dL, so as ANCA-MPO titter of 17 IU/mL and he had no haematuria or proteinuria. Clinically, the patient has no symptoms, regained weight and all his energy.

Conclusions:

Although still debated, current literature suggests that double positivity for ANCA and ANA/anti-dsDNA in AAV-GN may predict more severe renal outcomes. In this case, however, kidney recovery was achieved following induction therapy, indicating that the presence of positive ANA/anti-dsDNA does not necessarily predict a worse outcome. Differentiating AAV-GN from lupus nephritis can be challenging without a kidney biopsy. Clinical suspicion, prompt diagnosis, and appropriate treatment are critical for achieving the best outcomes.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.