Clinicopathological Features and Outcomes of IgA Nephropathy with Hematuria and/or Minimal Proteinuria

Background/Aims: Information regarding the clinical and histological prognostic factors of IgA nephropathy (IgAN) is mostly derived from patients in whom diagnostic renal biopsies were performed because their proteinuria levels were higher than 1-2 g/d. The clinicopathological features and outcomes of IgAN patients presenting with normal blood pressure, normal renal function, hematuria and minimal or no proteinuria are not well described. We therefore conducted a study of the clinicopathological features and outcomes in IgAN patients with these characteristics. Methods: The clinical, laboratory, and pathological manifestations and long-term outcomes of all IgAN patients with the above-mentioned characteristics were collected. The relationships between renal pathology, injury, long-term outcomes and clinical factors were studied, and the risk factors of IgAN were analyzed using multivariate logistic regression. Results: Of all of the renal biopsy cases, IgAN with the above features accounted for 8.9%. Among these patients, 67.2% (253) showed simultaneous hematuria and proteinuria, 23.1% (87) showed only hematuria, and 9.7% (36) showed only proteinuria. Additionally, 33.8% (127) patients showed macroscopic hematuria and 65.1% (245) had a prodromal infection. Regarding renal pathological changes, 45.5% (171) of the patients were unexpectedly classified as Grade II to IV (Hass classification). Proteinuria at the time of renal biopsy was an independent predictor of more severe renal pathological injury. After a median follow-up of 75 months, 61 (16.2%) patients experienced adverse events. Among these patients, 28 (7.45%) exhibited hypertension, 22 (5.85%) presented proteinuria levels >1 g/24 h, and 11 (2.9%) developed impaired renal function. Conclusions: Severe renal histological injury may be observed in some IgAN patients with benign clinical characteristics. Proteinuria is an independent predictor of severe renal pathological injury in IgAN patients with mild proteinuria. More severe pathological injury (> Grade II, Hass classification) are predictors of poor prognosis.