- Ab-agn complex deposition
- Most common cause of glomerulonephritis world wide
- Often at time of resp or gi infxn→ a period of IgA activation
- W/Renal involvement: UA + RBCs, protein; Urine microscopy w/rbc casts, dysmorphic RBCs
- Serum: decrease in GFR; often + c-anca; normal complement levels
- Definitive dx typically requires bx (proliferative GN w/IgA deposits)