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

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.