At first, Tyler developed red patches and raised spots that turned purple and looked like bruises all over his legs and buttocks. Then he complained that his stomach and knees hurt. When his parents took him to the doctor to find out what was wrong, the doctor said that Tyler had the classic signs of Henoch-Schönlein purpura.

About Henoch-Schönlein Purpura

Henoch-Schönlein purpura (pronounced: heh-nok shoon-line purr-puh-ruh) — usually just called HSP — is a condition that causes small blood vessels, or capillaries, to become swollen and irritated. This inflammation, called vasculitis, usually occurs in the skin, intestines, and kidneys. Inflamed blood vessels in the skin can leak red blood cells, causing a characteristic rash called purpura. Vessels in the intestines and kidneys also can swell and leak.

The disorder was named after two German physicians, Eduard Henoch and Johann Schönlein, who first described the disease in the 1800s. Sometimes it's also called allergic purpura or anaphylactoid purpura.

HSP occurs much more often in kids than in adults, usually happening between ages 2 and 11. It is one of the most common forms of vasculitis in children, and boys get it about twice as often as girls.

Causes

Although no one really knows what causes HSP, doctors do know that it occurs when the body's immune system doesn't function as it should. A protein called immunoglobulin A (IgA) is deposited into the blood vessels and sets off an immune reaction.

In most cases, HSP occurs after a child has had a bacterial or viral infection of the upper respiratory tract (sinuses, throat, or lungs). But certain medicines, food reactions, insect bites, and vaccinations also may cause it.

HSP cannot be passed from one person to another.