ANCA-associated vasculitis with dominant renal involvement: clinical and morphological presentation and outcomes
Authors: Dobronravov V. A. , Karunnaya A. V. , Kazimirchik A. V. , Smirnov A. V. 
Published: December 2019

THE AIM: The analysis of clinical and morphological presentations and outcomes of primary systemic vasculitis associated with anti-neutrophil cytoplasmic antibodies (ANCA-V) with dominant kidney involvement; the determination of clinical and morphological parameters associated with prognosis.

PATIENTS AND METHODS. Eighty nine patients with morphologically confirmed ANCA-associated kidney vasculitis on standard immunosuppressive therapy (IST) were included in this retrospective study. Clinical, immunological, and histological indices were analyzed at the time of the kidney biopsy, and early in the short-term (3-6 months) and in the long-term follow-up. The following outcomes were evaluated: the achievement of clinical and immunological remission of the disease; eGFR at the end of follow-up, the progression of renal disease (by the composite point: initiation of renal replacement therapy (RRT) or the estimated glomerular filtration rate (eGFR) <15 ml/min/1.73m2 or decrease in eGFR >50 %); all-cause mortality. The prognostic significance of clinical and morphological parameters was evaluated in multivariable regression models.

RESULTS. Most of cases (78 %) were represented by rapidly progressive or acute nephritic syndrome. Mean eGFR was 23 ml/min/1.73 m2. Fifteen percent of patients required acute dialysis. Dominant morphological phenotypes of glomerular lesions were sclerotic (34 %) and mixed (36 %) according to the International Pathology Classification (IPC). Median follow-up was 24 (8; 55) months. Cumulative 5-year and 10-year patient’s survivals and were 92 % and 86 %, respectively. Cumulative 5-year and 10-year renal survivals were 86 % and 68 %, respectively. The cumulative 5-year and 10-year proportions of cases without progression of kidney disease were 80 % and 55 %, respectively. Within 3-6 months of the induction IST 81 % of patients achieved clinical remission (complete (59 %) or partial (22 %)) (CR3-6), while 84 % of patients had immunological remission. Serum creatinine (Pcr) at the time of kidney biopsy was only the factor associated with the risk of renal progression (Expβ=1.73 (95 %CI 1.40-2.14) per 0.1 mmol/l increase). IPC classes and ANCA Renal Risk Score (ARRS) groups as well as other morphological indices of kidney injury had no independent associations with the renal outcomes in Cox models adjusted for Pcr. The independent factors associated with eGFR at the end of follow-up were: CR3-6 (β=0.36±0.08, p<0.001); age (β=-0.34±0.09, p<0.001), Pcr (β=-0.35±0.09, p<0.001) and the global glomerulosclerosis (β=0.28±0.08, p<0.001). CR3-6 (β=0.57±0.10, p<0.001), and the proportion of cellular crescents (β=0.26±0.12, p=0.023) and interstitial inflammation (β=0.27±0.11, p=0.026) were also independently associated with the change of eGFR by the end of follow-up.

CONCLUSION. An unfavorable renal prognosis for ANCA-V determined by severe renal dysfunction due to inflammatory and fibrotic alterations of the organ can be significantly improved by adequate therapy with the achievement of higher patient’s and kidney’s survival. The baseline serum creatinine is only the factor associated with the long-term risks of dialysis and kidney disease progression. In addition to baseline serum creatinine and the development of early clinical remission, the separate assessment of global glomerular sclerosis, cellular crescents, and interstitial inflammation may be more useful for the individual prediction of long-term eGFR changes than IPC classes or ARRS.