Allergic purpura

Allergic purpura is an allergic disorder. The joints (usually knees, ankles, hips, wrists, and elbows), the skin of the legs, thighs, and abdomen, the gastrointestinal tract, and the kidneys are involved. Allergic purpura can affect both sexes, all ages, but is more common in boys (2 to 8 years).

"Purpura" is a bleeding disorder that occurs when capillaries rupture, allowing small amounts of blood to accumulate in the surrounding tissues. In AP, this occurs because the capillaries are blocked by protein complexes formed during an abnormal immune reaction. The skin is the most obvious site of reaction, but the joints, gastrointestinal tract, and kidneys are also often affected.