The
diagnosis of anti-neutrophil cytoplasmic antibodies (ANCA)-associated
vasculitis (AAV) is often made in a context of emergency, and relies on
clinical presentation, positivity of ANCA antibodies and/or histological
documentation. The severity of residual organ damage, in particular chronic
kidney disease (CKD), depends on the precocity of diagnosis, the efficacy of
induction treatment, and on the prevention of AAV relapses. Recently, although
targeted therapy with rituximab have shown efficacy for the induction and
maintenance of remission in AAV,
residual organ damage and infectious complications are still penalizing
patients. The identification of reliable biomarkers could help personalize the
level and/or duration of immunosuppression (i.e., precision medicine).
Indeed, type and severity of organ involvement
are heterogenous among patients, and ANCA positivity can be missing in patients
with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) andeosinophilic granulomatosis with polyangiitis (EGPA). During follow-up, an
increase in proteinuria or an impairment of renal function can result from
chronic kidney disease progression, or from necrotizing pauci-immune crescentic
glomerulonephritis, so that chronic renal lesions can be difficult to
clinically discriminate from active vasculitis flare. In such setting, renal
biopsy is a valuable tool but remains an invasive procedure that cannot be
repeated easily.
The follow-up of ANCA positivity and of anti-proteinase 3
(PR3) or anti-myeloperoxidase (MPO) antibodies titers is, to date, the most
accurate biomarker available to evaluate disease activity and/or predict
relapses. Although several studies converge to show that severe flares were
very unlikely in patients with negative ANCA, the clinical utility of ANCA
follow-up to predict relapses is still debated, and no preemptive increase in
immunosupresssion is currently recommended in patients showing new ANCA
positivity or a rise in anti-PR3/anti-MPO titer.
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