PaediatricsPending review

IgA vasculitis (Henoch-Schönlein purpura)

IgA immune complexes deposit in small vessels throughout the body after a triggering infection, so the tetrad of purpura, joints, gut and kidneys is simply a map of which small-vessel beds the deposits happen to land in.

In a nutshell

IgA immune complexes deposit in small vessels after a triggering infection, damaging the vessel wall wherever they land. In the skin this produces palpable purpura over extensor/dependent surfaces; in joints, arthralgia; in gut, colicky pain (and a risk of intussusception); in the glomerulus, a mesangial IgA nephropathy-type glomerulonephritis that determines long-term prognosis. Most disease is self-limiting; renal follow-up is what matters.

Classic presentation

A 5-year-old, after a recent upper respiratory tract infection, develops palpable purpura over the extensor surfaces of the legs and buttocks with joint pain and colicky abdominal pain, normal platelets.

Key points

The rash is palpable (not a simple bruise) because of vessel wall inflammation, and gravity/pressure-dependent in distribution: extensor legs and buttocks.

You’ve reached the end of the preview

This topic is part of full high-yield access. Create a free account to read every key point, first-line investigation and exam trap — or browse the free sample topics without one.

Educational content pending clinical review. Not medical advice.