. 2019 Feb 28;17:10. doi: 10.1186/s12969-019-0311-z

Table 3.

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

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.