Why is Henoch-Schonlein purpura more common in children?

1. What is Henoch-Schönlein purpura?

Henoch-Schönlein Purpura (HSP), also known as IgA vasculitis, is an inflammatory disease of small blood vessels characterized by the deposition of immunoglobulin A (IgA). Typical symptoms include:

Purpura: a red or purple rash that is symmetrically distributed on the lower extremities;

Joint swelling and pain: mostly seen in knee and ankle joints;

Gastrointestinal symptoms: abdominal pain, vomiting, and in severe cases, intussusception;

Kidney damage: hematuria, proteinuria (occurs in about 30%-50% of children).

2. Epidemiological data of high incidence in childhood

Henoch-Schonlein purpura is the most common systemic vasculitis in children, with about 90% of cases occurring in children aged 2-11 years, especially in the 3-10 age group, with a male-to-female ratio of about 1.2:1. There are fewer cases in adults, and the symptoms may be more severe.

3. Key reasons for high incidence in childhood

1. Immature immune system

Overactive immune response: Children’s immune systems are in the “learning stage” and may overreact after exposure to pathogens. For example, after infection, the immune system releases a large amount of IgA antibodies, forming immune complexes that are deposited on the blood vessel walls and trigger inflammation.

Mucosal immunity is dominant: Children's intestinal and respiratory mucosal barriers are weaker, pathogens and allergens can more easily enter the blood and activate mucosal-related IgA immune responses.

2. Infection is the main cause

About 50%-70% of cases have a history of upper respiratory tract infection before the onset of the disease. Common triggers include:

Viruses: such as adenovirus, influenza virus;

Bacteria: Group A Streptococcus infections are particularly relevant;

Other pathogens: mycoplasma, parasites, etc.

After infection, pathogen antigens may mimic the body's own proteins, leading to cross-immune reactions (molecular mimicry mechanism).

3. More opportunities for allergen exposure

Food allergies: such as milk, eggs, seafood, etc.;

Drug reactions: antibiotics (such as penicillin), nonsteroidal anti-inflammatory drugs;

Environmental factors: pollen, dust mites, and mosquito bites.

Children have more exploratory behaviors and are more likely to be exposed to new foods and environments, which can easily trigger allergies.

4. Genetic susceptibility

Family tendency: Some children have a family history of autoimmune diseases (such as systemic lupus erythematosus);

Gene polymorphism: Genotypes such as HLA-DRB1*01 and HLA-B35 are associated with disease susceptibility.

5. Weak intestinal barrier function

Children have higher intestinal permeability, allowing pathogens and undigested proteins to enter the blood circulation more easily (the "leaky gut" phenomenon), promoting the formation of immune complexes.

4. Differences in prognosis between children and adults

Self-limiting tendency: Most cases in children recover within 4-6 weeks and only require symptomatic treatment (such as rest and analgesia).

Risk of kidney involvement: About 5% of children may develop chronic kidney disease and require long-term monitoring of urine routine.

Poor prognosis in adults: Adults are more prone to severe renal damage and relapse, which may be related to differences in immune regulation mechanisms.

V. Prevention and Management Recommendations

Avoid triggers: Treat infections promptly and reduce exposure to known allergens;

Regular follow-up: Monitor urine routine for at least 6 months after onset to detect kidney lesions at an early stage;

Healthy lifestyle: balanced diet, moderate exercise, and enhanced immunity.

Henoch-Schonlein purpura is common in children, which is the result of the combined effects of immune system development characteristics, infection exposure, genetic factors, etc. Although most children have a good prognosis, parents need to be alert to kidney complications, seek medical treatment in time and follow the doctor's advice. Through scientific protection and early intervention, the impact of the disease on children's health can be effectively reduced.

References:

- Chinese Medical Association Pediatric Branch Immunology Group "Guidelines for the Diagnosis and Treatment of Allergic Purpura in Children"

- Epidemiological study related to The Lancet (2019)

- A review of the mechanisms of IgA vasculitis from the National Institutes of Health (NIH)