The difficulty in considering modifiable pathology risk factors in children with IgA nephropathy: crescents and timing of renal biopsy.

The need for an early diagnosis of primary IgA nephropathy (IgAN) is particularly felt in children since they have a long life expectancy. However, IgAN has a slowly progressive course and renal function can even remain unchanged for decades. The long-term predictive value of modifiable risk factors, such as proteinuria and proliferative/inflammatory lesion at renal biopsy, remains unknown. Interest has focused on crescents, which represent a clear risk factor for renal vasculitides. A number of rare cases of extracapillary IgAN involving >40 % of glomeruli have been reported, but in most cases of IgAN crescents involve <10 % of glomeruli. The long-term effect of small non-circumferential crescents detected by chance or without a clinical picture of progressive IgAN is still unknown. The Oxford study failed to find a predictive value of crescents in either children or adults, and these results were confirmed by the recent VALIGA study on 1,147 patients with IgAN (174 children). A recent study reports a correlation between the time elapsed from the diagnosis of urinary abnormalities and renal biopsy which suggests that crescents are associated with disease onset and then likely undergo a healing process into sclerotic lesions, which are commonly detected in biopsies performed years after onset. The authors of this study propose that primary IgAN may have similarities with Henoch-Schoenlein purpura nephritis, which presents with acute glomerular damage, mesangial proliferation, endocapillary leucocyte infiltration and crescent formations, and that these lesions can undergo resolution with sclerotic healing. This hypothesis is highly suggestive of the silent progression of several cases of IgAN without clear clinical changes, stressing once more the need for a combined clinical and pathological evaluation of children with IgAN that considers both the underlying pathogenetic event and its possible evolution.