Henoch-Schonlein purpura is common in children between the ages of two and 10. The condition causes inflammation (swelling) of small blood vessels. The blood vessels then become easily broken and allow blood to leak. The bleeding into the skin causes a rash, which often looks more severe than it actually is. HSP does not usually cause much discomfort. On the other hand, if blood leaks into the kidneys, joints, or digestive tract, it can cause various problems, including kidney disease. Audio available.