What are the symptoms of allergic purpura

Allergic purpura is a relatively common skin disease. In fact, it is a hemorrhagic symptom of microvascular hypersensitivity. The causes are often drug allergy, pollen allergy, or infection, etc. After the onset of the disease, patients often have sore throat and upper respiratory tract infection. Patients will have fever, small urticaria on the skin, and polymorphic erythema.

Clinical manifestations

Symptoms and Signs

1) Prodromal symptoms: 1 to 3 weeks before the onset of the disease, there are often symptoms such as low fever, sore throat, upper respiratory tract infection and general discomfort.

2) Typical symptoms and signs Clinically, they vary depending on the location of the lesion.

(1) Skin symptoms: Symmetrical maculopapular purpura of varying sizes appears in batches near the large joints of the lower limbs and buttocks, recurring on the limbs and buttocks, with a few involving the face and trunk. Initially, the lesions are itchy, with small urticaria, angioedema and erythema multiforme.

(2) Joint symptoms: There may be single or multiple migratory joint swelling and pain or arthritis, sometimes with local tenderness. They often occur in the knee, ankle, elbow, wrist and other joints. There may be exudate in the joint cavity, but no sequelae are left. Clinically called articular type

(3) Gastrointestinal symptoms: About 2/3 of patients may experience paroxysmal abdominal colic or persistent dull pain, accompanied by vomiting, hematemesis, or bloody stools. Severe cases may have bloody stools. It is clinically called abdominal type.

(4) Kidney symptoms: Macroscopic hematuria, microscopic hematuria, proteinuria and tubular urine usually appear about 2 to 4 weeks after the onset of purpura. They may also appear after the rash subsides or when the disease is dormant. Recovery usually occurs within weeks. Severe illness may result in renal insufficiency, azotemia, and hypertensive encephalopathy. In a few cases, hematuria, proteinuria or hypertension may persist for more than 2 years. Clinically called renal type.

Pathogenesis

Chronic allergic purpura is a hemorrhagic disease caused by the body's allergy to a certain substance, which leads to damage to small blood vessels throughout the body. Bleeding may occur in the skin, mucous membranes, joint cavities or internal organs. Different symptoms appear depending on the location and degree of bleeding. Clinically, skin purpura is the main symptom, and there are often symptoms such as swollen and painful joints, abdominal pain, bloody stools, and hematuria. Some children have a tendency to relapse. There are two types of pathogenesis of chronic allergic purpura:

1. Immediate allergic reaction: Allergens combine with proteins in the body to form antigens. The produced IgE antibodies are adsorbed on mast cells, releasing histamine and slow-reacting substances (SRS-A). These substances cause dilation of arterioles and capillaries and increase vascular permeability.

2. Immune response: is caused by the formation of antigen-antibody complex. This type of soluble, small molecule complex can stimulate alkaliphilic granulocytes to release histamine and 5-hydroxytryptamine, and can also be deposited on the blood vessel walls and the basement membrane of the glomerulus to activate complement and cause tissue damage.