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Table 3 Histologic classification of IgA nephropathy of Haas (according to ref. [29])

From: Different histological classifications for Henoch-Schönlein purpura nephritis: which one should be used?

Haas classification Description
Class I – Minimal histologic lesion Glomeruli are normocellular, without segmental sclerosis, necrosis, or crescents.
Class II – Focal-segmental glomerulosclerosis (FSGS)-like Glomeruli show focal and segmental sclerosis without mesangial or endocapillary hypercellularity, crescents, or necrosis.
Class III – Focal proliferative glomerulonephritis 50% or fewer of the glomeruli (not including globally sclerotic glomeruli) are hypercellular. This hypercellularity may be limited to mesangial areas, or include endocapillary hypercellularity, crescents, or necrosis.
Class IV – Diffuse proliferative glomerulonephritis More than 50% of the glomeruli (not including globally sclerotic glomeruli) are hypercellular. This hypercellularity may be limited to mesangial areas, or include endocapillary hypercellularity, crescents, or necrosis.
Class V – Advanced chronic glomerulonephritis 40% or more of the glomeruli are globally sclerotic, and/or there is > 40% estimated tubular atrophy or loss in the cortex. If these criteria are met, the biopsy specimen is graded as class V regardless of other histologic features.
  1. Modified with permission from Elsevier Ltd.©