Marker for the renal vasculitis in children is –
IgA nephropathy or Berger's disease affects children and young adult and is perhaps the most frequent type of glomerulonephritis in children.

IgA nephropathy (Berger nephropathy) 

It is the most common type of glomerulonephritis worldwide.
Children and young adults are commonly affected.
It occurs after an upper respiratory tract infection or gastrointestinal infection.

Clinical presentation

Gross hematuria within 1-2 days after on upper respiratory tract infection. This feature distinguishes it from PSGN. In PSGN hematuria occurs 7-21 days after respiratory infection.
Can also present with nephritic or nephrotic syndrome.
Mild to moderate hypertension.

Pathology

Focal and segmental mesangial proliferation.
IgA deposition in the mesangium.
Serum complement level is normal. This feature also differentiates it from PSGN. In PSGN complement (C3) level is decreased.
Whereas IgA nephropathy is isolated renal disease, similar IgA deposits are also found in systemic disorders of children like Henoch shonlein purpura, which also has renal vasculitis as a component fit view of the high frequency of IgA nephropathy in children, IgA can be used as a marker for renal vasculitis.
Increased IgA level
Low complement level
↑ Antineutrophilic cytoplasmic antibody titre
Increase antinuclear antibody