[Persistent microhaematuria with negative or low proteinuria]

The level of proteinuria continues to be the clinical parameter that is best related to the development of long-term renal failure in glomerular pathologies. This quantity is particularly important when we analyse the progression of patients with IgA nephropathy. As such, the natural progression of patients with IgA who clinically present with normal kidney function, microhaematuria and low proteinuria had not been analysed comprehensively until the Spanish multicentre study herein analysed. After studying 141 Caucasian patients with biopsied IgA nephropathy and a "benign" clinical profile and after they were classified histologically in accordance with the new Oxford classification, it could be concluded that the renal prognosis of these patients was excellent. This is the first study in the literature that demonstrates the usefulness of this new classification in patients who clinically have normal renal function and proteinuria below 0.5 g/day. The latest advances in the genetics of this disease, as well as in the collaboration of complement pathways in its pathophysiology mean that these results cannot be extrapolated to all the populations studied. In addition, the analysis and follow-up of microhaematuria has regained importance as an independent prognostic factor for developing renal failure, although there are no consistent studies in this regard yet. However, it is a subject that should be examined again by the nephrology community.