Sydenham's Chorea

What causes Sydenham's chorea

After a group A streptococcal infection, usually strep throat, the immune system makes antibodies against the bacteria. In susceptible children, these antibodies also react with parts of the brain's basal ganglia, which control movement and behavior. This "molecular mimicry" disrupts movement control. Sydenham's chorea is one of the major Jones criteria for acute rheumatic fever, and can occur alone or alongside heart inflammation (carditis) and arthritis.

Rheumatic fever is now uncommon in the US but remains common in many low- and middle-income countries and some Indigenous communities.

Symptoms

Movement symptoms

• brief, irregular, purposeless movements that flow from one body part to another, often affecting the face, hands and feet
• worse with stress and absent during sleep
• clumsiness, dropping objects, deteriorating handwriting
• "milkmaid's grip": rhythmic squeezing and releasing when holding someone's hand
• difficulty keeping the tongue out ("darting tongue")
• slurred or explosive speech
• weakness and low muscle tone
• movements on one side in about 20% (hemichorea)

Behavioral and emotional symptoms

• emotional lability: sudden crying or laughing
• irritability and anxiety
• obsessive-compulsive symptoms
• attention problems and declining school performance

Parents and teachers sometimes first notice fidgetiness or clumsiness and mistake it for behavior problems.

Diagnosis

There is no single test. Diagnosis is based on:

• the typical movement pattern and history
• strep antibody tests: ASO and anti-DNase B titers, which may be normal if the infection was months earlier
• a throat swab, though often negative by the time chorea appears
• echocardiogram to look for rheumatic heart disease, which can be silent
• blood tests to rule out other causes: thyroid function, lupus antibodies, and others
• brain MRI in atypical cases

Other causes of chorea, such as lupus, hyperthyroidism, drug effects, Wilson disease and, in older people, Huntington's disease, are considered. See chorea.

Treatment

Eradicate strep and prevent recurrence

• an antibiotic course (usually penicillin) to clear any remaining strep
• long-term antibiotic prophylaxis, usually monthly benzathine penicillin injections or daily oral penicillin, for years, to prevent further rheumatic fever and heart damage. Duration depends on heart involvement, often until early adulthood or longer

Treat the movements

• mild chorea may need no medicine
• valproic acid or carbamazepine are commonly used
• antipsychotics such as risperidone or haloperidol are sometimes used but carry movement side effects
• corticosteroids may shorten the illness in moderate to severe cases
• IVIG or plasma exchange in severe, resistant cases

Support

• emotional and psychological support, and treatment for anxiety or OCD
• school accommodations, as handwriting and concentration may be affected
• occupational therapy for fine motor skills

Outlook

Most children recover within 1 to 6 months, though symptoms can last up to 2 years. About 20 to 40% have recurrences, often triggered by new strep infections or stress, and occasionally pregnancy or hormonal contraceptives in later life. The biggest long-term risk is rheumatic heart disease, which is why penicillin prophylaxis and heart monitoring matter.

Related condition: PANDAS

PANDAS/PANS describes sudden-onset obsessive-compulsive symptoms or tics after strep infection. Unlike Sydenham's chorea, it is debated and not part of rheumatic fever criteria.

Frequently asked questions

What is Sydenham's chorea?

It is a movement disorder in children causing involuntary, jerky movements, clumsiness and emotional changes. It develops weeks to months after a strep infection, when the immune response mistakenly affects part of the brain. It is a feature of acute rheumatic fever.

What are the symptoms of Sydenham's chorea?

Symptoms include irregular jerky movements of the face, hands and feet, clumsiness, worsening handwriting, slurred speech, weakness, emotional outbursts, anxiety and obsessive-compulsive behaviors. Movements stop during sleep.

Is Sydenham's chorea curable?

It usually resolves on its own within 1 to 6 months, sometimes longer. Medicines can reduce movements. Recurrences can happen, so long-term penicillin is used to prevent new strep infections and protect the heart.

Why is Sydenham's chorea also called St. Vitus' dance?

The name dates back to the Middle Ages, when people with involuntary dancing movements prayed to St. Vitus for healing. Thomas Sydenham described the childhood form in the 17th century.

Does Sydenham's chorea affect the heart?

Sydenham's chorea is part of rheumatic fever, which can damage heart valves. Many children with chorea also have carditis, sometimes without symptoms. An echocardiogram is recommended, and long-term penicillin protects against further heart damage.