Anaphylactoid purpura, Henoch-Schönlein vasculitis
What is Henoch-Schönlein purpura?
Henoch-Schönlein purpura is an acute or chronic vasculitis, which affects the small blood vessels of the skin, joints, gastrointestinal tract and kidneys. (Vasculitis is a patchy inflammation of the walls of small blood vessels.) This results in a skin rash and changes in the functioning of other affected areas of the body.
This distinctive syndrome was first described by Heberden (English physician, 1710-1801) before 1800. In the 1830s, Schönlein (German physician, 1793-1864) described the typical rash and joint changes. Then in the 1870s Henoch (German paediatrician and a scholar of Schönlein, 1820-1864) recognised the gastrointestinal and kidney changes.
What causes Henoch-Schönlein purpura?
The cause is not known. Allergy or drug sensitivity appears to be important in some patients.
The disease may follow an upper respiratory tract infection, sometimes caused by Streptococcal bacteria. However, there have been small outbreaks of the condition with no apparent cause.
Who gets Henoch-Schönlein purpura and who is at risk?
The syndrome may occur at any age. However, it is more common in children than in adults, with most cases occurring in children aged two to eight years.
Boys are affected twice as often as girls.
Symptoms and signs of Henoch-Schönlein purpura
The syndrome may start suddenly with the simultaneous appearance of several different signs of the disease. It may also start gradually, with the symptoms and signs appearing in sequence over a period of weeks. There can be various combinations of symptoms and signs.
Malaise (feeling unwell or uncomfortable) and a low-grade fever are present in about half of all cases.
The skin lesions are present in everyone diagnosed with this syndrome. The rash usually starts on the legs and buttocks, but may also involve the arms, the trunk and the face.
The appearance of the rash is extremely variable. The classic lesion starts as a small wheal or reddish, raised papule. These usually blanch (become pale) if pressure is applied to them. They later lose this feature and become purpuric or petechial. Purpura is a skin rash resulting from bleeding into the skin by small blood vessels. The individual purple spots of the rash are called petechiae.
The purpuric areas change from red to purple and eventually become reddish-brown and fade. The rash is often raised and can be felt if the skin is examined.
Raised wheals, resembling urticaria (hives) can occur on the scalp, eyelids, lips, ears, the backs of the hands and the tops of the feet, the back, the scrotum and the perineum (the area of skin between the anus and the genitals).
Arthritis occurs in two-thirds of affected children. Large joints, particularly the knees and ankles, are most often involved. The affected joints may be swollen, tender and painful on movement. Joint symptoms usually resolve within a few days without leaving any residual problems.
Gastrointestinal symptoms are present in more than half of affected children. The most common problem is colicky abdominal pain, which can be severe and is often associated with vomiting. In more than 50% of children, the stools contain blood and vomiting of blood may also occur.
The kidneys are involved in between 25 to 50% of children during the acute phase of the illness. (Occasionally, the kidneys become involved once other symptoms and signs have died down.) Due to inflammation of the small blood vessels in the kidney, patients may leak blood or protein into their urine. The nephrotic syndrome occasionally occurs: this is when a patient loses more than three grams of protein in the urine and becomes protein deficient. The decreased blood protein leads to a leakage of fluid from the blood vessels into the tissues and presents as swelling of the ankles (called ankle oedema) and the area around the eyes (called periorbital swelling). Most children who have kidney involvement recover fully. Some will continue to show abnormalities in the urine, and a few will develop chronic kidney disease within a few years of the acute phase of Henoch-Schönlein purpura.
Rarely, the central nervous system is involved and this can be serious. The child may have seizures, partial paralysis and coma.
An enlarged liver and spleen and enlarged lymph glands may occur during the acute phase.
How is Henoch-Schönlein purpura diagnosed?
Rash, arthritis and gastrointestinal and kidney signs and symptoms are characteristic of full-blown Henoch-Schönlein purpura.
Laboratory tests are not diagnostic, but may include abnormal kidney function tests, decreased haemoglobin levels and increased levels of C-reactive protein, a marker of systemic inflammation (of the body generally rather than a specific part). There is no specific test for this disease and the diagnosis is based on the clinical findings and the exclusion of other types of vasculitic diseases for which there are specific tests.
How is Henoch-Schönlein purpura treated?
There is no specific treatment. In the very rare instance in which a specific allergen (substance that causes an allergic reaction) is identified, that substance should then be avoided.
If the disease follows a bacterial infection, this should be treated with appropriate antibiotics.
The symptoms of arthritis, rash, hives, fever and malaise can be treated. Non-steroidal anti-inflammatory drugs will often relieve these.
Serious complications such as bleeding into the gut and obstruction of the gut can be managed with corticosteroids. These are also used in those patients with serious central nervous system or kidney involvement.
What is the outcome of Henoch-Schönlein purpura?
Very rarely, death can occur during the acute phase from complications involving the gut, the kidneys or the central nervous system.
Chronic kidney problems may sometimes develop in later life. About 25% of children with kidney involvement have abnormal urine sediment (traces of blood cells in the urine) for years, but their ultimate prognosis is good.
The outcome is excellent in the absence of significant kidney disease. The illness is often mild, lasting for a few days with only transient arthritis and few purpuric spots.
In more seriously affected children, the average duration of the illness is four to six weeks, but there may be recurrences. The illness may smoulder on for a year or more.
When to call the doctor
If your child develops an unexplained rash or joint pain, then you must see your doctor as soon as possible.
(Reviewed by Prof Helmuth Reuter, University of Stellenbosch and Tygerberg Academic Hospital)