Henoch-Schönlein purpura (HSP), now formally called IgA vasculitis, is not a straightforward genetic disease that passes from parent to child in a predictable pattern. It is a complex condition where multiple genes contribute a degree of susceptibility, but an environmental trigger, usually an infection, is needed to set the disease in motion. You won’t find a single “HSP gene,” but genetics clearly play a role in determining who gets it and how severe it becomes.
What the Genetic Research Shows
A systematic review of published genetic studies identified 45 separate studies examining variations in 39 different genes linked to HSP. Most of these genes are involved in immune responses, inflammation, or blood vessel regulation. No single gene mutation causes HSP the way, for example, a mutation in the CFTR gene causes cystic fibrosis. Instead, the genetic picture looks more like that of asthma or type 1 diabetes: dozens of small genetic variations each nudge your immune system toward a higher likelihood of overreacting in a specific way.
The strongest genetic associations involve the HLA system, a group of genes that help your immune system distinguish your own cells from foreign invaders. Specific HLA variants appear significantly more often in people with IgA vasculitis than in the general population. These include HLA-A*03, HLA-B*37, and several HLA-DRB1 variants (particularly DRB1*10, DRB1*12, and DRB1*14). Carrying one of these variants doesn’t guarantee you’ll develop HSP, but it does increase susceptibility.
Beyond the HLA system, researchers have found links to genes controlling cytokines (signaling molecules that drive inflammation), adhesion molecules (proteins that help immune cells stick to blood vessel walls), and components of the renin-angiotensin system, which regulates blood pressure and fluid balance. The sheer number of genes involved explains why HSP doesn’t follow a simple inheritance pattern.
How Genetics Influence Disease Severity
Some of the most clinically meaningful genetic findings relate not to whether someone develops HSP, but to how it behaves once it appears. Certain HLA variants are tied to specific complications. For instance, the HLA-DRB1*14:01 variant occurred in 17.5% of patients who developed kidney inflammation during their illness, compared to just 4.5% of those who did not. Other variants, including DRB1*04:02 and DRB1*10:01, showed stronger links to gastrointestinal involvement, the kind that causes severe belly pain and sometimes bowel complications.
This means two children with HSP might have very different experiences partly because of their genetic makeup. One might have a mild case limited to a skin rash and joint pain, while another develops serious kidney involvement, and the difference may trace back in part to which immune-system gene variants each child carries.
The MEFV Gene and Familial Mediterranean Fever
One notable genetic connection involves the MEFV gene, which encodes a protein called pyrin that helps regulate inflammation. Mutations in this gene cause familial Mediterranean fever (FMF), a condition characterized by recurring episodes of fever and inflammation. Multiple studies suggest that people with FMF-related MEFV mutations face an increased risk of developing IgA vasculitis. One specific variant, called E148Q, has been linked to both a higher risk of HSP and a greater chance of joint involvement during the disease.
This connection is especially relevant in populations where MEFV mutations are common, including people of Mediterranean, Middle Eastern, and Armenian descent.
Does HSP Run in Families?
It can, though familial cases are uncommon. A review of 418 children with HSP found that 8 families had two affected members. In one family, both a mother and daughter developed the condition. In the other seven, siblings were affected, including one pair of twin sisters. The researchers concluded that the incidence of HSP among family members of affected children appears higher than what you’d expect by chance alone.
Still, the vast majority of children diagnosed with HSP have no affected relatives. Having a sibling or parent with the condition raises your risk modestly, but most family members will never develop it. This pattern is consistent with a disease that requires both genetic susceptibility and the right environmental trigger at the right time.
The Role of Infections and Other Triggers
Genetics load the gun, but an environmental trigger typically pulls it. The most common triggers are infections. Streptococcal bacteria are the best-documented culprit, but HSP has also been linked to viral infections including chickenpox, measles, hepatitis A and B, Epstein-Barr virus, and mycoplasma. Vaccines, certain medications, food allergies, and even insect bites have been implicated in some cases.
The prevailing theory is that these triggers provoke an abnormal immune response in genetically susceptible people. Specifically, the body produces a defective form of the antibody IgA1 that is missing certain sugar molecules on its surface. This “galactose-deficient” IgA1 clumps into immune complexes that deposit in the walls of small blood vessels, particularly in the skin, gut, joints, and kidneys. The deposits trigger inflammation, which produces the hallmark rash (palpable purpura), abdominal pain, joint swelling, and, in some cases, kidney damage. Genetic variations in the enzymes responsible for adding those sugar molecules to IgA1 may partly explain why some people produce the defective form and others don’t.
Ethnicity and Prevalence Patterns
HSP affects children of all backgrounds, but incidence rates vary by population, which further supports a genetic component. A nationwide Korean study covering 2006 to 2015 found an annual incidence of about 56 per 100,000 children under 18, with a peak incidence of roughly 122 per 100,000 in children around age 5. Studies from European and North American populations generally report lower rates, typically in the range of 10 to 20 per 100,000 children. These differences likely reflect a combination of genetic predisposition across populations and differences in environmental exposures, though study methods also vary.
What This Means in Practical Terms
If your child has been diagnosed with HSP and you’re wondering whether your other children are at risk, the honest answer is: slightly more than the general population, but the absolute risk remains low. There is no genetic test that predicts HSP, and no screening is recommended for siblings. The condition resolves on its own within a few weeks in most children, though kidney function is typically monitored for several months afterward because kidney involvement can emerge or worsen after the initial illness fades.
If your family has a history of familial Mediterranean fever or carries known MEFV mutations, that connection is worth mentioning to your child’s doctor, as it may affect how aggressively they monitor for complications. For everyone else, HSP remains a condition where bad genetic luck meets a common infection at a vulnerable moment, and the overwhelming majority of affected children recover completely.