Biomarkers to predict kidney outcomes in children with IgA vasculitis

Immunoglobulin A (IgA) vasculitis (IgAV, also known as Henoch-Schoenlein purpura, HSP) is a small vessel vasculitis, most commonly presenting in childhood. In most, it has a straightforward, self-limiting disease course, however some children may develop kidney involvement (IgAV-N) which occurs 4-12 weeks following disease onset and remains the biggest contributor to long-term morbidity. Therefore, children undergo a six-month period of kidney monitoring to identify nephritis via surrogate markers including urinalysis and blood pressure measurements. On-going efforts aim at earlier identification and prevention of nephritis during the window of opportunity between disease onset and established nephritis. By identifying those at highest risk of developing poorer kidney outcomes, the number of children developing chronic kidney disease stage 5 (CKD5) as a result of IgAV-N may be reduced. This review summarizes the latest scientific evidence that support the use of novel biomarkers which may allow nephritis to be identified earlier compared to traditional markers, as well as the risk stratification of children with established IgAV-N. These biomarkers may also enhance the evolving understanding of underlying inflammatory pathways. Promising novel urinary markers of early nephritis include angiotensinogen, Gd-IgA1, various complement proteins, and MCP-1, and serum markers such as α-SMA, C-Met, PTX-3, MMP-9, MRP 8/14, and adiponectin may help identify those at risk of developing CKD5. Prospective, longitudinal, international validation studies are required to investigate these markers further, including exploration of implementation into clinical practice.