Anaphylactoid purpura

Henoch-Schönlein purpura (HSP) is a rare condition in which blood vessels become inflamed. It typically results in a rash and joint and tummy pain.

HSP can affect people of any age, but the majority of cases occur in children under 10.

The medical term for inflammation of the blood vessels is vasculitis. Blood vessels throughout the body become irritated and swollen, which can cause problems such as bleeding into the skin (resulting in a rash) and occasionally problems affecting the kidneys and bowel.

HSP is not usually serious and most cases get better within a few weeks.

Signs and symptoms

The main symptoms of HSP are:

• a skin rash (purpura) that looks like small bruises or reddish-purple spots, usually on the buttocks, around the elbows and on the legs, and sometimes also on the face and upper body
• pain in the joints such as the knees and ankles, which can also become swollen, tender and warm
• tummy pain, which can develop suddenly before the rash appears

HSP can also cause some other symptoms, including passing blood in your urine or stools, vomiting and diarrhoea.

The condition is often associated with a previous infection (see below), so you or your child may initially have symptoms of an infection as well, such as a high temperature (fever) and feeling generally unwell.

Possible complications

HSP will usually get better on its own without causing any further problems, but occasionally it can lead to potentially serious complications.

The main complications associated with HSP are problems affecting the kidneys, which may not occur until several weeks or months after the other symptoms have passed. This can cause:

• blood in your urine
• protein in your urine – you won't be able to see this yourself, but it can sometimes cause your urine to become "frothy"
• high blood pressure (hypertension)
• swelling (oedema), particularly around the eyes and ankles

These symptoms eventually get better in most people, but in a small proportion the kidneys can stop working properly (kidney failure).

HSP can also sometimes cause other problems, such as swelling and pain in the testicles (orchitis) or an abnormal folding in the gut (intussusception) that can lead to a blockage in your bowel.

What causes HSP?

HSP is caused by a problem with your immune system, possibly as a result of a previous infection.

It has been known to occur after a bacterial or viral infection of the throat, airways or lungs (respiratory tract infection).

HSP cannot be spread from person to person and doesn't usually run in families.

Diagnosing HSP

Your GP may suspect HSP based on your symptoms and medical history. To confirm a diagnosis, you may need to be referred to a hospital doctor for the following tests:

• blood tests – to see how well the kidneys are working, or to look for recent signs of infection
• urine dipstick test – this is used to detect traces of blood or protein in the urine, as these are signs of a problem with the kidneys
• blood pressure tests – high blood pressure can also be a sign that the kidneys are affected
• skin biopsy – a very small sample of skin is sent to the laboratory to be examined under a microscope (this is only usually done if the doctor is not certain whether it is HSP)

If kidney problems are suspected, an ultrasound scan of your tummy and kidneys may also be carried out and you may have a kidney biopsy. This is where a small sample of kidney cells are removed using a needle that is inserted into your lower back.

Treating HSP

HSP is not usually serious. Most people can be treated at home with only occasional appointments to monitor the condition, although in severe cases admission to hospital may be necessary.

The rash, joint pain and tummy pain will usually get better over days or weeks without any treatment.

Anti-inflammatory medicines such as ibuprofen may help relieve joint pain if needed, but you should check with your doctor before using these as they shouldn't be taken by people with kidney or bowel problems. Paracetamol may be a suitable alternative and resting can also help.

A steroid medication such as prednisolone can sometimes help severe tummy pain.

Follow-up

Due to the risk of kidney problems, you or your child's urine and blood pressure will need to be tested regularly during and after treatment.

This may be done during trips to your GP or visits from a community nurse, although you may sometimes be asked to check your child's urine yourself and seek further advice if the results suggest there is a problem. 

The exact timing of these tests can vary, but they will usually start off being daily (if testing is done at home) or weekly at first and become less frequent over time. If no problems develop, monitoring can usually stop after around six months.

If any problems are detected, you or your child will be referred to a specialist for further tests and any necessary treatment.

Testing your or your child's urine

If you are asked to check your or your child's urine, you will be given containers to use and a special dipstick that detects small amounts of blood or protein in urine.

Your doctor or a nurse will tell you how to use these and how often a urine sample should be tested.

You'll need to collect a urine sample first thing in the morning, as this gives the most accurate reading.

Your doctor or nurse will talk to you about what the results of the test mean and what you should do if they suggest there is a problem.

When to seek medical advice

Regardless of your dipstick results, you should contact your GP, nurse or hospital if you or your child:

• pass red, rusty or blood-coloured urine
• pass stools with blood in them
• develop very painful and swollen joints
• develop severe tummy pain
• have swollen or painful testicles

Outlook

HSP usually gets better on its own within about four to six weeks and doesn't generally cause any lasting problems.

However, the condition can sometimes be severe and long-lasting – particularly in adults – and some people will get it more than once.

Kidney problems usually pass without any complications or need for treatment, but in rare cases kidney failure or permanent kidney damage can develop. This is why it's important to check for any early signs of a problem with regular urine tests, as instructed by your doctor.