HSP will usually get better on its own without causing any further problems, but occasionally it can lead to potentially serious complications.
The main complications associated with HSP are problems affecting the kidneys, which may not occur until several weeks or months after the other symptoms have passed. This can cause:
- Blood in your urine
- Protein in your urine – you won't be able to see this yourself, but it can sometimes cause your urine to become "frothy"
- High blood pressure (hypertension)
- Swelling (oedema), particularly around the eyes and ankles
- These symptoms eventually get better in most people, but in a small proportion the kidneys can stop working properly (kidney failure).
- HSP can also sometimes cause other problems, such as swelling and pain in the testicles (orchitis) or an abnormal folding in the gut (intussusception) that can lead to a blockage in your bowel.
HSP is caused by a problem with your immune system, possibly as a result of a previous infection.
In Henoch-Schonlein purpura, some of the body's small blood vessels become inflamed, which can cause bleeding in the skin, abdomen and kidneys. Why this initial inflammation develops isn't clear. It may be the result of the immune system responding inappropriately to certain triggers.
Nearly half the people who have Henoch-Schonlein purpura developed the disease after an upper respiratory infection, such as a cold. Infectious triggers may include chickenpox, strep throat, measles and hepatitis. Other triggers may include certain medications, food, insect bites or exposure to cold weather.