Immunoglobulin A vasculitis (IgAV), formerly called Henoch-Schönlein purpura, is a necrotizing small-vessel vasculitis of unknown etiology that predominantly occurs in children but can also occur in adults. It is characterized by IgA-immune complex and C3 and fibrin deposition in small vessels: primarily capillaries, postcapillary venules, and occasionally arterioles in affected organs. The annual incidence in childhood is 3-26 per 100 000 whereas in adults it is much lower at 0.1-1.8 per 100 000. It is seen more frequently in males, White individuals, and those of Asian descent.

IgAV is seasonal, with most childhood cases occurring during fall and winter. In adults, cases can also occur in summer months. Episodes can often be preceded by an upper respiratory infection.

IgAV is characterized clinically by palpable purpura, abdominal pain, arthritis, and hematuria. Adults are more likely to have joint symptoms and renal dysfunction. Children are more likely to have fevers and abdominal pain. There are prodromal symptoms of malaise, headache, and arthralgias. An individual episode may persist for 3-6 weeks, with recurrences in many patients.

Severe abdominal pain, vomiting, hematemesis, diarrhea, and hematochezia may indicate gastrointestinal involvement in 50%-75% of patients. An involved inflamed and edematous bowel may be accompanied by appendicitis, ileus, and infarction. Intussusception and bowel perforation are rare in adults.

Joint abnormalities may accompany the eruption with severe pain and sometimes swelling, warmth, and tenderness. Ankles and knees are most often involved; symptoms are often transient and migratory.

Renal involvement is common but is usually self-limited, with only a fraction of patients progressing to chronic renal failure or end-stage renal disease; these patients often have baseline renal dysfunction. The risk of renal failure is higher in adult patients and in those presenting with nephrotic or nephritic syndrome.