Henoch-Schönlein purpura (HSP) is a disease that causes small blood vessels in the skin to leak because of inflammation.

HSP can occur any time in life, but it usually happens in children between the ages of 2 and 11.

The causes of HSP are not fully understood. One theory is that it may develop as an immune response to an infection. Once the immune cells have rid the body of the germ cells, they continue to attack other cells in the body. This theory is based on the fact that, in many cases, HSP symptoms recur or worsen during upper respiratory infections. HSP has also been associated with insect bites and exposure to cold weather. Other cases have developed after a person received vaccination for typhoid, measles, cholera, hepatitis B, or yellow fever. Some foods, drugs, or other chemical toxins may trigger HSP as well. Often no cause can be found.

HSP has four main symptoms:

• Rashes and bruising. Leaking blood vessels in the skin cause rashes that look like bruises or small red dots to develop on the legs, buttocks, and back of the arms. The rash may first look like hives, then change to look like bruises. Rarely, the rash may spread to the upper part of the body, but it is usually on the parts of the body that “hang down,” like the legs, buttocks, elbows, and even earlobes. The rash does not disappear or turn pale when you press on it.
• Abdominal pain. About two-thirds of people with HSP experience pain in the stomach that may cause vomiting or blood in the stool. This pain and bleeding can vary from mild to severe.
• Arthritis. About 80 percent of people with HSP have pain and swelling in their joints, usually in the knees and ankles, less frequently in the elbows and wrists. These joint symptoms have no long-lasting effects, although they can be very uncomfortable while they’re present.
• Kidney involvement. Blood in the urine (hematuria) occurs in about 40 percent of people with HSP. Often the blood cannot be seen by the naked eye, but it can be measured with a laboratory test called a urinalysis. In most people the hematuria goes away without permanent kidney damage. Protein in the urine or development of high blood pressure (hypertension) suggests more severe kidney problems.

In most cases, HSP lasts 4 to 6 weeks, with no long-term consequences. Sometimes symptoms come and go during this time period. About one in three people have more than one episode (recurrence) of HSP. Recurrences usually occur within a few months and are usually less severe than the initial episode. Even when it lasts longer than a few months, HSP can still resolve completely.

There is no specific treatment for HSP. The main goals of treatment are to relieve symptoms such as joint pain, abdominal pain, or swelling. In most cases, you can use over-the-counter medicines, such as acetaminophen (Tylenol), for the pain. In some patients with severe arthritis, the doctor may prescribe prednisone, a steroid medicine.

Between 20 and 50 percent of children with HSP develop some kidney problems, but only 1 percent progress to total kidney failure. Progression to kidney failure may take as long as 10 years. Your doctor will check your kidney function with blood and urine tests even after the main symptoms of HSP disappear. People who develop kidney disease usually show signs within 3 to 6 months after the initial rash appears. These immunosuppressive drugs may be prescribed to keep kidney disease from progressing to permanent kidney failure. A person with severe kidney failure must receive a blood cleansing treatment called dialysis or a kidney transplant if the damage is permanent.

Another rare complication of HSP is intussusception of the bowel, or intestine. With this condition, a section of the bowel folds into itself like a telescope. The bowel may become blocked as a result. Prednisone may be prescribed by your doctor, or the problem may need to be corrected with surgery.