No, Proteinuria is Not Always Present in IgA Nephropathy
Not all patients with IgA nephropathy develop proteinuria, though it is present in the majority of cases. IgAN can present with isolated hematuria without proteinuria, and approximately 23% of patients present with hematuria alone 1.
Clinical Presentation Patterns
IgAN demonstrates variable clinical presentations:
- Isolated hematuria (23%): Patients can have IgAN with only microscopic or macroscopic hematuria and no proteinuria 1
- Hematuria with proteinuria (67%): The most common presentation combines both findings 1
- Isolated proteinuria (10%): Less commonly, patients present with proteinuria alone 1
- Incidental detection (60%): Many cases are discovered incidentally on routine urinalysis 2
Diagnostic Implications
The 2025 KDIGO guideline emphasizes that kidney biopsy should be considered in all adults with proteinuria ≥0.5 g/day when IgAN is suspected 3. However, this threshold-based recommendation does not mean proteinuria is always present. The guideline encourages a more liberal biopsy policy for early diagnosis, recognizing that IgAN can present with varying degrees of proteinuria or none at all.
Prognostic Significance of Minimal or Absent Proteinuria
Patients presenting with minimal or no proteinuria generally have excellent long-term outcomes:
- 15-year renal survival of 93.8% in patients with proteinuria <0.5 g/day at diagnosis 4
- 100% five-year renal survival in patients with persistently mild proteinuria (<1 g/day) 5
- Only 2.9% developed impaired renal function during median 75-month follow-up in patients with hematuria and minimal proteinuria 1
Important Caveat
Despite benign clinical presentation, 45.5% of patients with minimal proteinuria showed Grade II-IV pathological injury on biopsy 1. This underscores that absence of significant proteinuria does not guarantee mild histologic disease. Proteinuria at biopsy is an independent predictor of more severe renal pathological injury 1, 6.
Treatment Goals When Proteinuria is Present
When proteinuria develops, the 2025 KDIGO guideline lowered the treatment target from <1 g/day to <0.5 g/day, ideally <0.3 g/day 3. This reflects evidence that even low-grade proteinuria (0.5-1.0 g/day) significantly increases risk of adverse kidney outcomes (hazard ratio 1.73-2.87) and accelerates eGFR decline by -1.02 mL/min per year 7.
Achieving proteinuria remission rapidly (<6 months) and maintaining stable control correlates strongly with improved prognosis, with 10-year kidney survival of 86% when proteinuria remains in target range >50% of the time versus only 45% when never achieving target 8.