Allergic Purpura Health Article

Definition

Allergic purpura (AP), a form of vasculitis (inflammation of the blood vessels), is a disease characterized by inflammation of the small arterial vessels (capillaries) in the skin, kidneys, and intestinal tract. Symptoms include a purple spotted skin rash, abdominal pain, gastrointestinal upsets, and joint inflammation, swelling, and pain. Although the exact cause of the disease is unknown, it often develops following a recent viral or bacterial infection of the respiratory tract and is an abnormal reaction of the immune system to the infection.

Description

AP may occur suddenly, or it may develop slowly over a period of weeks. The characteristic rash is always present in the disease. The rash begins as areas of redness and as small hives, which may develop anywhere on the body, but especially on the legs and buttocks, and may itch. The rash is caused by inflamed capillaries rupturing, allowing small amounts of blood to accumulate in the surrounding tissues. Through time the rash changes color from red to a bruised, purple color. Each rash spot will last about five days, and the rash can reoccur several times. The skin rash is the most obvious symptom of AP but is not the most serious, for the joints, gastrointestinal tract, and kidneys may also be affected.

Joint inflammation (arthritis), especially of the knees and ankles, occurs in two-thirds of the children affected by AP. The joints become swollen, tender, and painful with movement; the pain may be debilitating. However, the arthritis usually clears up with no permanent damage.

Gastrointestinal symptoms are a result of inflammation and bleeding of the capillaries in the gastrointestinal tract, including the mouth, esophagus, stomach, and intestines. Most children with AP experience severe abdominal pain, vomiting (possibly with blood), and bloody stools.

The most serious complication of AP is kidney inflammation (nephritis), which occurs in almost half of older affected children. Symptoms include blood and protein in the urine. Most children whose kidneys are affected recover fully, but about 10 percent later develop more serious chronic kidney disease. In 80 percent of those with kidney involvement, the kidney disease develops within the first four weeks of illness.

Children younger than three years who contract AP have a shorter, milder course of the disease with fewer recurrences. Older children are more likely to have more serious symptoms.

AP is also called Henoch-Schonlein purpura, named after the two German physicians who first recognized and described it in the 1880s. AP is also referred to as anaphylactoid purpura or vascular purpura.