Rheumatic fever is not hereditary in the traditional sense, meaning it doesn’t pass directly from parent to child through a single gene. But genetics play a significant role in who develops it. Twin studies show that identical twins share a 44% concordance rate for rheumatic fever, compared to just 12% in fraternal twins. That gap points to a strong genetic component in susceptibility, even though the disease itself requires an environmental trigger: an untreated strep throat infection.
What Genetics Actually Contribute
Rheumatic fever develops when the immune system overreacts to a group A streptococcal infection and mistakenly attacks the body’s own tissues, particularly the heart, joints, and brain. This happens through a process called molecular mimicry. Proteins on the surface of the strep bacteria closely resemble proteins found on heart valve tissue and nerve cells. In most people, the immune system clears the infection without incident. In genetically susceptible individuals, the immune system produces antibodies that can’t tell the difference between the bacterial proteins and the body’s own cells, triggering inflammation in the heart, joints, or nervous system.
Several specific immune system genes influence whether this misdirected attack occurs. The most studied are HLA genes, which help the immune system distinguish between foreign invaders and the body’s own tissue. Certain variants of these genes are significantly more common in people who develop rheumatic fever. In one study of Latvian children, carrying specific HLA gene combinations increased the odds of developing rheumatic fever by three to eleven times compared to children without those variants. Different combinations were linked to different complications: some variants correlated with heart valve damage affecting multiple valves, while others were associated with Sydenham’s chorea, the neurological form of the disease that causes involuntary movements.
Beyond HLA genes, variations in a gene called MBL2, which produces a protein involved in the body’s first line of immune defense, also affect risk. People who produce high levels of this protein appear more likely to develop rheumatic heart disease specifically. One study found that a particular MBL2 gene variant that lowers protein production was actually more common in people who had rheumatic fever without heart involvement, suggesting it may be protective against the cardiac complications.
How Strong Is the Genetic Influence?
The clearest evidence comes from twin studies. A systematic review and meta-analysis pooled data across multiple studies and found that when one identical twin developed rheumatic fever, the other twin did too 44% of the time. For fraternal twins, who share only about half their genes (like any siblings), that number dropped to 12%. The odds of both twins being affected were over six times higher for identical pairs than fraternal pairs.
That 44% concordance rate in identical twins is revealing in two directions. It confirms genetics matter considerably, since identical twins share the same DNA and their rate is nearly four times higher than fraternal twins. But it also confirms genetics aren’t the whole story, since more than half of identical twins with an affected sibling never develop the disease themselves. If rheumatic fever were purely genetic, you’d expect concordance close to 100% in identical twins.
The Environmental Side of the Equation
You cannot develop rheumatic fever without first having a group A strep throat infection that goes untreated or inadequately treated. That’s the non-negotiable environmental trigger. But the conditions that lead to strep exposure and repeated infections also matter.
A longitudinal cohort study tracking children over time found that large family size was one of the strongest risk factors, increasing the likelihood of rheumatic fever in both early and middle childhood. Household overcrowding was a significant factor for children who developed the disease later in childhood. A history of recurrent throat or ear infections, which signals repeated strep exposure, also raised risk substantially. Children who moved neighborhoods or attended new group settings like private nurseries had higher rates in early childhood, likely because mixing with new peer groups exposes children to unfamiliar strep strains their immune systems haven’t encountered.
The socioeconomic picture is more complex than you might expect. In early childhood, rheumatic fever was actually associated with markers of higher socioeconomic status, possibly because those children had more exposure to group settings. In later childhood, the pattern reversed: overcrowding and indicators of lower socioeconomic status became the dominant risk factors. The common thread isn’t poverty or wealth per se, but proximity to peers carrying strep bacteria.
What Runs in Families
If a parent or sibling had rheumatic fever, you haven’t inherited the disease, but you may have inherited immune system genes that make you more susceptible to the same misdirected immune response after a strep infection. Families also tend to share the same living conditions, household size, and exposure patterns that facilitate strep transmission, so the familial clustering of rheumatic fever reflects both shared genetics and shared environments.
There is no genetic test currently used to screen for rheumatic fever susceptibility. Diagnosis still relies entirely on clinical criteria. The Jones criteria, last revised in 2015, require evidence of a recent strep infection plus a combination of characteristic signs: heart inflammation (detected clinically or by echocardiogram), joint inflammation, involuntary movements, a distinctive rash, or small nodules under the skin. No blood test or genetic panel can tell you in advance whether you’ll develop rheumatic fever after a strep infection.
Prevention if Your Family Is Affected
The most important preventive step is straightforward: treat strep throat promptly with antibiotics. This is true for everyone but especially relevant if rheumatic fever runs in your family. Strep throat is common in school-age children, and not every sore throat is strep, but a rapid strep test or throat culture can confirm it quickly.
For someone who has already had one episode of rheumatic fever, prevention of recurrence becomes critical. Each subsequent strep infection carries a high risk of triggering another attack, and the risk of heart damage increases with repeated episodes. The standard approach is long-term antibiotic prophylaxis, typically an injection every three to four weeks or a daily oral regimen, continuing at least until age 21. The duration depends on whether heart damage occurred during the initial episode and how many years have passed since the last attack. The risk of recurrence is highest in the first few years after the initial episode and gradually declines over time.
For family members who haven’t had rheumatic fever themselves, there’s no recommendation for prophylactic antibiotics. The practical takeaway is vigilance about sore throats in children, especially in households where someone has a history of the disease, and making sure confirmed strep infections are treated fully.