The four main characteristics of Henoch-Schonlein purpura include:

• Rash (purpura). Reddish-purple spots that look like bruises develop on the buttocks, legs and feet. The rash can also appear on the arms, face and trunk and may be worse in areas of pressure, such as the sock line and waistline.
• Swollen, sore joints (arthritis). People with Henoch-Schonlein purpura often have pain and swelling around the joints — mainly in the knees and ankles. Joint pain sometimes precedes the classical rash by one or two weeks. These symptoms subside when the disease clears and leave no lasting damage.
• Digestive tract symptoms. Many children with Henoch-Schonlein purpura develop belly pain, nausea, vomiting and bloody stools. These symptoms sometimes occur before the rash appears.
• Kidney involvement. Henoch-Schonlein purpura can also affect the kidneys. In most cases, this shows up as protein or blood in the urine, which you may not even know is there unless you have a urine test done. Usually this goes away once the illness passes, but some people develop persistent kidney disease.

When to see a doctor

See your doctor if you have Henoch-Schonlein purpura and it's causing serious problems with your digestive tract.

If your child develops the rash associated with this condition, see your doctor as soon as possible.

In Henoch-Schonlein purpura, some of the body's small blood vessels become inflamed, which can cause bleeding in the skin, abdomen and kidneys. It's not clear why this initial inflammation develops. It may be the result of the immune system responding inappropriately to certain triggers.

Nearly half the people who have Henoch-Schonlein purpura developed it after an upper respiratory infection, such as a cold. Other triggers include chickenpox, strep throat, measles, hepatitis, certain medications, food, insect bites and exposure to cold weather.

Factors that increase the risk of developing Henoch-Schonlein purpura include:

• Age. The disease mainly affects children younger than 10.
• Sex. Henoch-Schonlein purpura is slightly more common in males than in females.
• Race. White and Asian children are more likely to develop Henoch-Schonlein purpura than are black children.

For most people, symptoms improve within a month, leaving no lasting problems. But recurrences are fairly common.

Complications associated with Henoch-Schonlein purpura include:

• Kidney damage. The most serious complication of Henoch-Schonlein purpura is kidney damage. This risk is greater in adults than in children. Occasionally the damage is severe enough that dialysis or a kidney transplant is needed.
• Bowel obstruction. In rare cases, Henoch-Schonlein purpura can cause intussusception — a condition in which a section of the bowel folds into itself like a telescope, which prevents matter from moving through the bowel.

Your doctor will be able to diagnose the condition as Henoch-Schonlein purpura if the classic rash, joint pain and digestive tract symptoms are present. If one of these signs and symptoms is missing, your doctor may suggest one or more of the following tests.

Lab tests

No single laboratory test can confirm Henoch-Schonlein purpura, but certain tests can help rule out other diseases and make a diagnosis of Henoch-Schonlein seem likely. They may include:

• Blood tests. Your blood may be tested if your diagnosis isn't clear based on your signs and symptoms.
• Urine tests. Your urine may be tested for evidence of blood, protein or other abnormalities to determine if your kidneys are still working properly.

Biopsies

People who have Henoch-Schonlein purpura often have deposits of a certain protein, IgA (immunoglobulin A), on the affected organ. Your doctor may take a small sample of skin so that it can be tested in a lab. In cases of severe kidney involvement, your doctor may suggest a kidney biopsy to help guide treatment decisions.

Imaging tests

Your doctor may recommend an ultrasound to rule out other causes of abdominal pain and to check for possible complications, such as a bowel obstruction.

Henoch-Schonlein purpura usually goes away on its own within a month with no lasting ill effects. Rest, plenty of fluids and over-the-counter pain relievers may help with symptoms.

Medications

Corticosteroids, such as prednisone, may help shorten the time and intensity of joint and abdominal pain. Because these drugs can have serious side effects, discuss the risks and benefits of using them with your doctor.

Surgery

If a section of the bowel has folded in on itself or ruptured, surgery may be needed.

Home care focuses on keeping people with mild Henoch-Schonlein purpura comfortable while the disease runs its course. Rest, plenty of fluids and over-the-counter pain relievers may help.

You'll likely first see your family doctor or your child's pediatrician for this condition. You may later be referred to a kidney specialist (nephrologist) if kidney complications develop. Here's some information that may help you get ready for your appointment.

What you can do

Before your appointment, write answers to the following questions:

• When did the symptoms begin?
• Did they come on suddenly or gradually?
• Was the person with the rash (you or your child) sick before the rash started?
• What medications and supplements does the person with the rash take regularly?

Questions you may want to ask your doctor include:

• What might be causing these symptoms?
• What tests are needed to confirm the diagnosis?
• Is this condition temporary or chronic?
• How will I know if there's kidney damage? What if it turns up later?
• How is Henoch-Schonlein purpura treated?
• What are the side effects of treatment?
• Do you have any literature on this condition? Can you recommend a website where I can learn more?

What to expect from your doctor

Your doctor is likely to ask a number of questions, such as:

• What did the rash look like when it first started?
• Is the rash painful? Does it itch?
• Does the person with the rash have other symptoms, such as stomach pain or joint aches?