IgA nephropathy and IgA vasculitis nephritis: Case

This boy has IgA nephropathy. The diagnosis rests on the synpharyngitic timing of the macroscopic haematuria, the normal C3 and C4 which exclude post-infectious glomerulonephritis, and the biopsy showing dominant mesangial IgA deposition with IgG and C3. The Oxford score of M1 E1 S0 T1 C0 places him at moderate risk of progression, driven mainly by the T1 component and his proteinuria of 0.9 g per day, which sits just below the 1 g per day threshold that defines the high-risk category. ^[1]

Clinical findings

The defining clue is the temporal relationship between the haematuria and the sore throat. In IgA nephropathy the macroscopic haematuria is synpharyngitic, appearing within one to two days of the mucosal infection, whereas post-infectious glomerulonephritis waits one to two weeks and is accompanied by a low C3 and an elevated ASO. This boy's haematuria began on the same morning as the sore throat, his C3 and C4 are normal, and his ASO is not elevated, which together point firmly to IgA nephropathy and away from post-infectious disease. ^[1]

The proteinuria of 0.9 g per day is the most important prognostic variable, because sustained proteinuria over 1 g per day is the single strongest predictor of progression to end-stage kidney disease. His blood pressure at the 95th centile adds a second adverse marker. The Oxford score of M1 E1 S0 T1 C0 confirms the moderate risk: the T1 component reflects early tubulointerstitial scarring, which is the strongest histological predictor of long-term progression. The E1 component marks active, potentially steroid-responsive endocapillary inflammation. ^[2]