What is Henoch-Schönlein purpura (HSP)?

Henoch-Schönlein purpura (HSP) is an autoimmune disease (the immune system attacks the body). In the case of HSP, the small blood vessels in the skin become inflamed (a condition called vasculitis) and start leaking red blood cells, which causes a purplish, bruise-like rash on the legs, buttocks, and arms. HSP also affects the gastrointestinal tract and frequently the kidneys which can cause a cramping pain in the abdomen.

In addition, HSP:

  • can occur at any age, but it most often affects children between the ages of 2 and 11.
  • is the most common form of pediatric vasculitis (approximately 20 cases per 100,000 children per year).
  • tends to affect boys more often than girls.
  • is not contagious.

Who is affected by HSP?

HSP is the most common acute vasculitis affecting children, with an incidence of approximately 10 cases per 100,000 children per year. Although the syndrome is usually seen in children, people of any age may be affected. It is more common in boys than in girls.

What are the symptoms of Henoch-Schönlein purpura (HSP)?

Typical HSP skin rash

The main symptom of HSP is a painless rash (purpura) that usually appears on the legs, buttocks, and arms (though it can occur elsewhere). The rash starts off as red dots, then turns purple over a period of three to six days and looks like bruises. The rash does not change color when it is pressed on.

The symptoms of HSP are often preceded by cold and flu symptoms, such as fever, headache, nausea, loss of appetite, or diarrhea.

Aside from the rash, the other main symptoms of HSP are:

  • Abdominal pain: Approximately two-thirds of children with HSP have abdominal pain, which may be accompanied by vomiting. Occasionally, blood may appear in a child’s vomit or stool. Blood in vomit or stool is a medical emergency and should be checked out by a doctor immediately. Rarely, patients develop an abnormal bowel folding called intussusception.
  • Joint pain: Children with HSP often have swelling and tenderness in the knees, ankles, elbows, and wrists. The swelling usually lasts 1-3 days. Sometimes whole limbs will swell. The inflammation does not cause crippling arthritis.

Boys with HSP may also have painful swelling in the scrotum.

HSP can also affect the kidneys, and patients may have small amounts of blood in the urine. Between 20 and 50% of children with HSP have problems with their kidneys. The majority of these kidney problems resolve (get better) over 6 months.

Symptoms usually last between 2 - 12 weeks, typically about a month. Recurrences are not frequent but do occur.

What causes Henoch-Schönlein purpura (HSP)?

The causes of HSP have not been identified. However, children who get HSP often have a cold or respiratory infection such as strep throat beforehand. In cases of HSP, the child’s immune system attacks the body’s cells during the respiratory infection, then continues the attack even after the infection is gone.

HSP has also been linked to insect bites and exposure to cold weather. In addition, it may be a reaction to some vaccinations, foods, drugs, or chemicals.