IgA vasculitis (Henoch-Schonlein purpura)

IgA vasculitis, formerly called Henoch-Schonlein purpura, is inflammation of small blood vessels driven by deposits of an antibody called IgA, in which the immune system appears to involve these vessels in the skin, joints, gut, and kidneys. Current research describes the underlying process as beginning with an abnormally structured form of IgA1 that the body has trouble clearing, which then forms immune complexes that deposit in small vessels and trigger local inflammation and tissue injury.

It is described as the most common systemic vasculitis in children, frequently appearing after an upper respiratory infection and often resolving on its own, though it can also occur in adults, in whom the disease tends to run a more severe course. Precise population-wide prevalence figures are limited and vary by region and by how cases are counted, and research notes that incidence appears to be genetically and environmentally influenced, with cases clustering somewhat more often in the autumn and winter months.

Common signs

A raised purplish rash (purpura), usually on the lower legs and buttocks, joint pain and swelling, abdominal pain, and sometimes kidney involvement seen as blood or protein in the urine.

This is a plain-language summary for orientation, not a diagnosis. Mechanisms are described as current understanding, not settled fact. Work with your own clinician for your care.