Allergic Purpura Health Article

Symptoms

The onset of AP may be preceded by a headache, fever, and loss of appetite. Most children first develop an itchy skin rash. The rash is red, either flat or raised, and may be small and freckle-like. The rash may also be larger, resembling a bruise. Rashes become purple and then rust-colored over the course of a day, and fade after several weeks. Rashes are most common on the buttocks, abdomen, and lower extremities. Rashes higher on the body may also occur, especially in younger children.

Joint pain and swelling is common, especially in the knees and ankles. Abdominal pain occurs in almost all children with AP, along with blood in the stools. About half of all affected children show blood in the urine, low urine volume, or other signs of kidney involvement. Kidney failure may occur due to widespread obstruction of the capillaries in the filtering structures called glomeruli. Kidney failure develops in about 2–5 percent of all affected children and in 15 percent of those with elevated blood or protein in the urine.

Less common symptoms include prolonged headache, fever, and pain and swelling of the scrotum, scalp, eyelids, lips, ears, backs of the hands and feet, and perineum. Involvement of other organ systems may lead to heart attack (myocardial infarction), inflammation of the pancreas (pancreatitis), intestinal obstruction, bowel perforation, or acute intussusception (a twisting inversion of the lining of the bowel).

Diagnosis

Diagnosis of AP is based on the symptoms and their development, a careful medical history, and blood and urine tests. X rays or computed tomography (CT) scans may be performed to assess complications in the bowel or other internal organs. In some cases a renal biopsy may be useful to determine the extent of kidney involvement.

When to call the doctor

A doctor should be consulted if a child exhibits symptoms of AP. After a child has had an episode of AP, the doctor should be called if the child experiences sudden increases in abdominal pain, which may indicate a bowel infarction or perforation, or if the child exhibits decreased urine output, indicating kidney disease.

Treatment

Most cases of AP resolve completely without treatment. Nonetheless, a hospital stay with supportive treatment is usually required because of the possibility of serious complications. Non-aspirin pain relievers may be given for joint pain. Corticosteroids (such as prednisone) are sometimes used to alleviate gastrointestinal tract inflammation but have not been shown to be effective for associated kidney problems. Kidney involvement requires monitoring and correction of blood fluids and electrolytes. Salt intake should be restricted. A child with AP should be monitored until abnormal urinary findings subside.

Children with severe kidney complications may require a kidney biopsy so that tissue can be analyzed. Even after all other symptoms subside, elevated levels of blood or protein in the urine may persist for months and require regular long-term monitoring. Hypertension or kidney failure may develop months or even years after the acute phase of the disease. Kidney failure requires dialysis or transplantation.

Surgery may be necessary to correct acute intussusception of the bowel.

Prognosis

AP may be mild, lasting only two or three days. However, for those children with moderate to severe symptoms, AP may last for four to six weeks, with relapses in about half of all children within six weeks, especially if the child contracts another respiratory infection or is exposed to the allergic agent. Relapses can occur up to seven years after the initial disease. Full recovery occurs in most cases without kidney involvement. However, one fourth of children who have kidney symptoms still have detectable problems years later. There is a higher likelihood of permanent renal damage with a higher number of recurrences.

Prevention

If the initiating trigger for a case of AP is identified in an affected child, everything possible should be done to ensure that the child is not exposed to that substance again. If the cause is thought to be a bacterial infection, such as strep throat, prophylactic antibiotic treatment is sometimes given once the infection has been treated to prevent recurrence.