Henoch-Schonlein purpura (HSP) is disease that causes small blood vessels to become swollen and irritated—a condition called vasculitis.
It is most common in children between the ages of 3 and 15 years old and is rarely seen in adults. HSP is not contagious and tends to affect boys more than girls.
The actual cause of HSP is not known. About half the time, however, children who get HSP have a cold or respiratory infection such as strep throat beforehand. HSP has also been linked to bug bites, cold weather, and some vaccinations.
Signs & Symptoms
Usually, the first sign of HSP is a rash called palpable purpura that appears as dark reddish splotches on the feet, legs, and buttocks. A child with HSP may also have joint pain, abdominal pain, and/or kidney problems.
Nearly every child diagnosed with HSP has a painless rash. The rash usually starts as raised wheals, reddish blotches, and little red dots (petechiae) around the feet and ankles. The rash may also be on the legs and buttocks. In smaller children—especially those who do not yet walk—the rash is often seen on the arms, trunk, and face. The rash usually takes about 10 days to fade.
The majority of children with HSP experience joint pains. Children typically only have a few affected joints—hips, knees, and ankles. While the joints may swell for 1-3 days, there is no permanent damage.
About 50% of children with HSP will have abdominal pain. Abdominal problems may be fairly mild (e.g., nausea, vomiting, and mild pain). In rare occasions, abdominal problems are much more serious and involve gastrointestinal bleeding or intussusception. Intussusception is when the intestine folds in on itself and may become blocked. Abdominal pain tends to come on about a week after the rash first develops.
About 25% to 50% of children with HSP will have kidney problems. Usually, kidney problems due to HSP begin within days to 6 weeks after the rash first appears.
The most common kidney problem seen is blood in the urine. Blood is the urine is not usually visible to the naked eye. About 10% of the time, the urine becomes red or brown from blood. Up to 50% of patients also lose protein in the urine, and about 20% of the time protein lost is excessive.
Excessive loss of protein in urine requires the help of a pediatric nephrologist. Losing a lot of protein means a child is at risk for more serious problems—kidney damage and high blood pressure. Sometimes a pediatric nephrologist will perform a kidney biopsy to look at how severely a HSP affects a child’s kidneys.
The diagnosis of HSP is almost always based on symptoms. Your pediatrician may do blood and urine tests to help rule out other conditions and to check kidney function. There is not a specific blood test to diagnose HSP. An abdominal ultrasound may be done in patients with severe abdominal pain. In patients who have partial or unusual symptoms, a biopsy of the skin or the kidney may help make the diagnosis.
HSP is a mild illness, so it is usually treated with rest, fluids, and over-the-counter pain medicines such as acetaminophen (Tylenol). In severe cases, a child may need to be hospitalized.
Once the symptoms of HSP disappear, children should have their urine checked for blood and protein for at least 6 months after they are first diagnosed—even if their urine was normal at first. This is to make sure that the disease did not damage a child’s kidneys and that they are working properly. Sometimes, HSP in the kidneys persists or comes later and may need additional treatment.
Most of the time, HSP improves and goes away completely within a month. Sometimes HSP relapses; this is more common when a child’s kidneys are involved. If HSP does come back, it is usually less severe than the first time.
The long-term prognosis of HSP largely depends on whether the kidneys have been involved and, if so, how severe the involvement is.