Henoch-Schönlein nephritis in children and adults. Morphological features and clinicopathological correlations.

Rheumatoid purpura or Henoch-Schönlein syndrome is an IgA vasculitis affecting small vessels. The acute disease progresses by successive flare-ups of limited duration. Long-term prognosis depends mainly on the degree of initial renal damage. A review of the literature shows that renal involvement occurs in about 33% of children and 63% of adults with rheumatoid purpura. The most typical manifestation is segmentary focal glomerulonephritis, always associated with granulous IgA deposits in the mesangium. When renal signs are severe enough to warrant renal biopsy (generally at urine protein > 1 g/d and/or organic renal failure) the risk of developing chronic renal failure is 18% in children and 28% in adults. The best prognostic features are histological. The percentage of crescents, the presence of interstitial fibrosis and the presence of dense sub-epithelial deposits are correlated with risk of chronic renal failure. This risk is high (47%) in children with crescents in more than half the glomeruli. In adults, the percentage of crescents associated with unfavorable course appears to be lower than 50%. Predictions are only valid if no further renal flare-up occurs. In addition, histology cannot precisely predict the course of persistent renal sequelae. The severity of sequelae determines the risk and the rapidity of developing chronic renal failure. It is thus recommended to follow patients with Henoch-Schönlein nephritis for long periods.