Henoch-Schönlein Purpura (HSP) is an autoimmune disorder that is due to the production of autoantibodies against some of the body’s own antigens. It occurs most commonly in children between the ages of 2 and 11 years.
HSP results from an autoimmune vasculitis, resulting in the swelling and leakage of intravascular fluid from small blood vessels. It is the most frequently seen vasculitic condition to occur in children, though it does occur in adults as well.
The most well-known symptom is a skin rash consisting of raised purplish spots. Other organs that are affected by this pathologic condition include the kidneys, the joints and the digestive tract.
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Whilst a single microorganism has not been confirmed as the cause of HSP, the reason for the formation of autoantibodies may be one that causes an upper respiratory tract infection. Such a history is present in 30-50% of HSP patients. Other identified precipitating factors include:
- Other infectious agents
- Certain foods
- Some drugs
- Some insect bites
- Cold temperatures
Genetic factors may also play a role.
The symptoms of HSP are diverse:
- Skin manifestations: small red raised dots which later turn into bruises
- Gastrointestinal tract: nausea and vomiting, abdominal pain, blood in stools
- Joints: pain and inflammation
- Kidneys: blood in the urine in the acute stage, proteinuria or hypertension in later stages
In one of every three people with HSP, the first sign may be abdominal pain or joint pain, with the rash appearing up to 2 weeks later.
Though HSP itself is a relatively short-lived disease, it may have sequelae such as:
- Renal disease
- Renal failure
- Hypertension complicating pregnancy in women who had a prior episode of HSP
- Bowel intussusception
Diagnosis and Management
When the characteristic rash is present along with at least one of the following clinical features, HSP is suspected:
- Abdominal pain
- Joint pain
- Subcutaneous deposits of autoantibodies
- Hematuria or proteinuria which is confirmed by urine testing
The clinical diagnosis may be confirmed by a skin biopsy from the antibody deposits, or by a renal biopsy. Treatment is symptomatic, with measures also being directed at the prevention of renal damage.
Non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids are effective in controlling the joint pain and inflammation. Corticosteroids also relieve the abdominal pain. Intussusception requires emergency surgical treatment.
Renal damage in HSP requires a combination of corticosteroids to suppress the autoimmune reaction and the consequent inflammation by inhibiting the immune response. In addition, immunosuppressant therapy is required to shut down immune function and prevent the production of further autoantibodies.
Hypertension that occurs as a result of renal disease because of HSP is treated by two classes of drugs: angiotensinogen-converting enzyme (ACE) inhibitors, and angiotensin receptor blockers (ARBs). These are especially preferred because they not only bring down the blood pressure but also improve kidney function. Other anti-hypertensive drugs may also be required to help control hypertension.
The renal function in these patients must be followed up for at least 6 months after the episode subsides.
Most patients with HSP undergo a complete recovery. In 15% of children it may result in long-term kidney damage. 1% of this group will develop end-stage renal disease requiring dialysis or transplantation. The percentage of adults who go into chronic kidney disease is as high as 40% when they are followed up for 15 years.