What is Henoch–Schönlein purpura?
Henoch–Schönlein purpura (HSP) is a form of leukocytoclastic or small-vessel vasculitis, most often observed in children. It is sometimes called anaphylactoid purpura.
HSP results from inflammation of the small blood vessels in the skin and various other tissues within the body.
It generally affects children, but it may also occur in adult life. The most common symptoms include a vasculitic rash, joint pain, and abdominal pain. It may affect the kidneys and in some instances this leads to irreversible kidney damage. However, most cases resolve without treatment or long-term consequences.
Who gets HSP?
75% of cases occur in children under the age of 10 years. It is thought by most researchers to be more common in girls, although some have found a male predominance or both sexes to be equally affected. HSP may occur in adults and when it does, it is often more severe and kidney damage is more common than is the case in children. There does not appear to be any racial predilection. The incidence in the UK is approximately 20/100000 children (under 17 years old) per year, and is thought to be similar in New Zealand.
15 to 40% of children have at least one recurrence.
What causes HSP?
Although the precise cause is unknown, clinical evidence points to an infectious aetiology. The peak incidence of pediatric HSP is during the autumn and winter months. It often preceded by an upper respiratory tract infection, and is found to cluster within families. Beta-haemolytic streptococci are often found on throat swab or there is positive streptococcal serology on blood testing.
A multitude of other associations have been reported, including medications. These include: ACE inhibitors, angiotensin II receptor antagonists, clarithromycin and nonsteroidal anti-inflammatories.
The underlying mechanism of small blood vessel inflammation is the deposition of IgA immunoglobulin within the blood vessel walls. This leads to leucocytoclastic vasculitis. A subtle defect of IgA may predispose people to developing HSP.
What are the symptoms?
Henoch Schönlein purpura
The classic presentation is with a tetrad of symptoms and signs:
- abdominal pain
- kidney impairment
The symptoms are usually preceded by 2-3 weeks of fever, headache, muscle/joint aches, or abdominal pain.
A rash is present in virtually all cases. It usually starts as red spots or bumps (which may have a ‘hive-like’ appearance) which rapidly change to small dark purple bumps (palpable purpura) within the first 24 hours. The most common sites of involvement are the lower legs, buttocks, elbows and knees. The rash is symmetrical and may even become generalised. Blisters and/or ulcers may develop in the affected areas.
Arthritis (joint inflammation) is present in 75% of cases and usually involves one to four joints, especially the ankles and knees. It may be transient and move between different joints.
Abdominal pain is present in half to three-quarters of patients and precedes the rash in up to one third. There may be associated diarrhoea and bleeding from the bowel. Orchitis and interssusception are possible complications.
Kidney involvement is seen in up to 50% of cases. It is usually mild and self-limiting, however it is important that it is diagnosed and followed up as persistent impairment may occur. It normally occurs within a few days to one month after the onset of the other symptoms. Approximately 10% have serious kidney problems at presentation, 15% are left with subtle abnormalities in their urine tests, and 1-5% progress to end-stage kidney failure long term.
Rarely involvement of other organs such as the lungs, brain, and heart occurs.
What tests should be performed?
The diagnosis is often obvious if the classic symptoms are present.
- A blood and urine test should be performed to look for any signs of kidney involvement. These tests should be repeated at regular intervals initially to ensure kidney impairment is not developing or worsening.
- Blood pressure should be measured at the same time.
- A skin biopsy is often not necessary especially in children, but may be performed to confirm the diagnosis.
What is the treatment?
In the majority of cases, no specific treatment is required and the rash fades over one week. Recurrent crops of lesions occur over the next 6–16 weeks in up to one-third of cases. Five to ten per cent may even have persistent disease.
- Non-steroidal-anti-inflammatory-drugs (eg, ibuprofen) are effective at relieving joint and abdominal pain.
- In more severe cases, oral steroid medication is often used.
- Other options include dapsone or colchicine.
- If significant kidney involvement is present, steroids are usually combined with more potential immunosuppressives or intravenous immunoglobulin.