What are the symptoms of allergic purpura?

Henoch-Schönlein purpura (HSP) is a small-vessel inflammatory disease that primarily affects the skin, joints, gastrointestinal tract, and kidneys. Typical symptoms include joint pain and swelling, skin purpura, abdominal cramps, bloody stools, blurred vision, and others. A detailed analysis is as follows:

1. Joint pain and swelling: HSP may cause joint pain and swelling, typically affecting the knees and ankles. Symptoms include pain, swelling, and limited mobility in the affected joints. However, permanent joint damage is uncommon. Joint symptoms may appear before the onset of skin purpura but usually last no more than 1–2 days.

2. Skin purpura: Patients develop red or purple spots on the skin. These spots are typically neither painful nor itchy and most commonly appear on the lower extremities, especially the calves and feet. They may also occur on the arms, face, and trunk.

3. Abdominal cramps: As a form of vasculitis primarily affecting small blood vessels, HSP can involve capillaries in the mucosa of the digestive tract and visceral peritoneum. This may lead to intestinal inflammation, edema of the intestinal wall, bleeding, necrosis, or even perforation, resulting in abdominal pain.

4. Bloody stools: Vasculitic reactions in the intestinal wall can increase vascular permeability, causing blood leakage into the gut lumen. This leads to symptoms such as abdominal pain, diarrhea, and hematochezia. The bleeding may be mild, detectable only through stool testing, or severe enough to be visibly apparent.

5. Blurred vision: In rare cases, when HSP affects the eyes, it may cause inflammation of ocular blood vessels, impacting the retina and optic nerve, thereby leading to blurred vision.

In daily life, symptoms of HSP may resolve spontaneously within weeks or months, but recurrence is possible. If any of the above symptoms occur, prompt medical attention is recommended for accurate diagnosis and appropriate treatment.