Characterization of early IgA nephropathy.

Histological grading of 45 patients with clinical early immunoglobulin A (IgA) nephropathy was correlated with disease progression over a median follow-up of 123 months. Clinical early IgA nephropathy was defined as a serum creatinine level of 1.3 mg/dL or less, proteinuria of 0.4 g/d or less of protein, and the absence of hypertension at the time of renal biopsy. Disease progression was related to the occurrence of impaired renal function, increased proteinuria, and hypertension. We applied a previously described chronicity-based histological grading to the renal biopsy specimen and also assessed acute glomerular lesions. Disease progression was observed in 44.4% of these patients. Forty patients (89%) showed glomerular grade 1 (GG1) and 5 patients (11%) showed GG2, but this grading did not correlate with disease progression. However, when GG1 was subdivided into GG1a (mean sclerosis per glomerulus <10%) and GG1b (mean sclerosis per glomerulus 10% to <25%), GG1a correlated with nonprogressive disease. Tubulointerstitial grade also correlated with disease progression but was associated with a low sensitivity for predicting nonprogressive disease. Hyaline arteriolosclerosis and acute glomerular lesions did not correlate with disease progression. The chronicity-based histological grading is not only applicable to clinical early IgA nephropathy, but also more importantly, it characterizes GG1a in a subset of patients with a very low risk for disease progression, which can be regarded as genuine early IgA nephropathy.