Henoch-Schonlein purpura (HSP) is an inflammation of the blood vessels in the skin and other body organs. Skin involvement often results in a rash, typically occurring on the buttocks and legs. The rash often resembles bruising or bleeding into the skin, a condition referred to as “purpura.”

People of all ages may develop HSP, but it is most common in children.

The exact cause of HSP is unknown. It is believed to be a disorder of the immune system. It may be triggered by bacterial or viral infections, certain medications, vaccines, or perhaps even insect bites. HSP frequently occurs in the spring, often after a respiratory infection. It is not contagious.

A risk factor is something that increases your chance of getting a disease or condition. Risk factors for HSP include:

• Recent upper respiratory illness, such as a cold
• Age: 2 to 11
• Recent exposure to vaccines, chemicals, cold weather, or insect bites
• Sex: male children are twice as likely as females to develop the disease; the risk is equal in adults.

Symptoms may last for 4 to 6 weeks. These may include:

• Skin rash of reddish-purple spots, usually on the buttocks or legs, occasionally on the elbows that is not itchy
• Pain in the joints, especially knees and ankles
• Abdominal pain
• Blood or protein in the urine caused by kidney inflammation
• Swelling of the ankles
• Swelling of the scrotum in males
• Fever
• Blood in the stool
• Vomiting

Your doctor will ask about your symptoms and medical history, and perform a physical exam. Tests may include:

• Blood tests
• Urinalysis
• Stool sample
• Skin biopsy from an area of the rash

HSP usually gets better on its own. However, under some circumstances your doctor may prescribe specific medications to reduce symptoms and prevent complications. These may include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs)—to lessen joint pain and arthritis
• Cortisone medication—for significant abdominal pain or kidney disease
• Antibiotics—to treat infection
• Cyclophosphamide ( Cytoxan )—to suppress the immune system when you have symptoms of severe kidney disease