Résumé
Obesity is a poor prognostic factor in autoimmune diseases and a risk factor for chronic kidney disease. A low BMI can also be deleterious in these affections. We studied the impact of BMI on the presentation and evolution of ANCA vasculitis (AAV) with renal involvement. The new BMI (nBMI), which provides a more accurate estimation of weight status, was preferred to the standard BMI.Methods: we conducted a multicentric retrospective study including patients with AAV with histologically proven renal involvement between 2010 and 2021. Renal biopsies were reviewed blinded to clinical data. The association between nBMI, the occurrence of end-stage kidney disease (ESKD), mortality, relapses and treatment-related adverse events were analysed.Results: 85 patients were included and classified according to their nBMI: 31 normal weight, 29 overweight and 25 obese. Anti-PR3 antibodies were more frequent in the overweight group (p=0.029). There were no other differences, particularly in clinical presentation, severity of initial renal damage and induction treatment. Histological data were similar between groups. During follow-up, the occurrence of ESKD, adverse events and renal relapses were less frequent in overweight group (p=0.037; 0.036; 0.036 respectively). At 5 years, survival without death or ESKD was significantly better in overweight group (p=0.041). In multivariable analysis, overweight was protective against the occurrence of the composite ofdeath or ESKD compared to a nBMI < 25 [HR 0.334 (95% CI 0.133-0.836) p=0.019] after adjustment forsex and ANCA type.Conclusion: being overweight according to nBMI is associated with a better overall prognosis in AAV with renal involvement.