Variations in Urinary Renin-Angiotensin-Aldosterone Component Concentrations in Paediatric IgA Vasculitis Nephritis

IgA Vasculitis (IgAV) is the most common form of vasculitis in children, and 1–2% of patients develop chronic kidney disease. In other forms of glomerulonephritis, there is strong evidence to support the role of the renin-angiotensin-aldosterone system (RAAS); however, data are lacking in IgAV nephritis. This study evaluated urinary RAAS components in children with IgA vasculitis, both with nephritis (IgAVN) and without nephritis (IgAVwoN). Urinary concentrations of renin, angiotensinogen and aldosterone were quantified using ELISAs. In total, 40 patients were included: IgAVN n = 9, IgAVwoN n = 17, HC n = 14, with a mean age of 8.3 ± 3.3 years. Urinary renin demonstrated no trend with nephritis. Urinary angiotensinogen was statistically significantly elevated in IgAV (1.18 ± 1.16 ng/mmol) compared to HC (0.28 ± 0.27 ng/mmol, p = 0.0015), and IgAVN (2.00 ± 1.22 ng/mmol) was elevated compared to IgAVwoN (0.74 ± 0.89 ng/mmol, p = 0.0492) and HC (p = 0.0233). Urinary aldosterone levels were significantly elevated in IgAV (1236 ± 1438 pg/mmol) compared to HC (73.90 ± 65.22 pg/mmol, p < 0.0001); this was most increased in IgAVwoN patients (1793 ± 1507 pg/mmol; IgAVN 183.30 ± 111.30 pg/mmol, p = 0.0035, HC p < 0.0001). As expected, the RAAS system is activated in patients with IgAVN and, more surprisingly, even in those without active nephritis. Further studies are needed to fully understand the role of the RAAS system in IgA vasculitis.