Rheumatic Fever: Causes, Symptoms, and Treatment

What is Rheumatic Fever?

Rheumatic fever is an inflammatory disease that can develop as a complication of untreated or inadequately treated strep throat or scarlet fever. It's caused by group A Streptococcus bacteria, specifically Streptococcus pyogenes. Rheumatic fever primarily affects children between 5 and 15 years old and can cause long-term damage to the heart, including damaged heart valves.

Causes and Risk Factors

Rheumatic fever is not directly caused by the Streptococcus bacteria, but rather by the body's immune response to the infection. The immune system mistakenly attacks healthy tissues, particularly in the heart, joints, skin, and central nervous system.

Risk factors for developing rheumatic fever include:

• Living in poverty or crowded conditions
• Being between 5 and 15 years old
• Genetic predisposition (HLA-DR7 or HLA-DR53)
• Exposure to group A Streptococcus bacteria
• Living in certain geographic areas (e.g., Salt Lake City, Utah in the United States)

The Immune Response in Rheumatic Fever

Rheumatic fever involves both innate and adaptive immunity. The adaptive immune response includes both humoral (B-cell) and cellular (T-cell) immunity. The key mechanism behind rheumatic fever is molecular mimicry or cross-reactivity.

The M protein of group A Streptococcus is similar to proteins found in human heart tissue, joints, and other organs. When the immune system attacks the M protein, it may also attack these similar human proteins, leading to tissue damage.

Pathology of Rheumatic Fever

The characteristic pathological finding in rheumatic fever is the Aschoff nodule or Aschoff body. These nodules consist of:

• Central fibrinoid necrosis
• Surrounding reactive histiocytes (called Anitschkow cells)

Aschoff nodules are typically found in the heart but can also occur in other affected tissues.

Signs and Symptoms: The Jones Criteria

The diagnosis of rheumatic fever is based on the Jones Criteria, which include major and minor manifestations.

Major Criteria

1. Carditis: Inflammation of the heart, including endocarditis, myocarditis, and pericarditis. This can lead to heart failure if severe.

2. Polyarthritis: Migratory joint inflammation affecting multiple large joints. The arthritis is typically severe but resolves without permanent damage.

3. Subcutaneous nodules: Painless, firm lumps under the skin, similar to those seen in rheumatoid arthritis.

4. Erythema marginatum: A distinctive rash with pink rings and pale centers, usually on the trunk or limbs.

5. Sydenham's chorea: Rapid, uncoordinated jerking movements primarily affecting the face, hands, and feet.

Minor Criteria

• Fever
• Elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)
• Joint pain
• Leukocytosis
• Prolonged PR interval on ECG

Diagnosis

To diagnose rheumatic fever, clinicians typically look for:

• Two major criteria, or
• One major criterion and two minor criteria

Additionally, evidence of a recent streptococcal infection is required, which can be demonstrated by:

• Elevated or rising antistreptolysin O (ASO) titer
• Positive throat culture for group A Streptococcus
• Positive rapid Streptococcus antigen test

Diagnostic Tests

1. ASO titer: Measures antibodies against streptolysin O. A titer > 400 Todd units is considered positive.

2. Anti-DNase B: Another antibody test, less reliable than ASO but useful in cases of skin infections.

3. Electrocardiogram (ECG): May show PR interval prolongation (first-degree heart block).

4. Chest X-ray: Can reveal an enlarged cardiac silhouette in cases of pancarditis.

5. Echocardiogram: Useful for detecting valvular heart disease.

Complications

Rheumatic fever can lead to several serious complications:

1. Rheumatic heart disease: Chronic valvular heart disease, particularly affecting the mitral and aortic valves.

2. Heart failure: Due to severe carditis.

3. Atrial fibrillation: Can occur in patients with mitral stenosis.

4. Stroke: From embolization of valve vegetations.

5. Recurrent rheumatic fever: Increases the risk of permanent heart damage.

Treatment

The treatment of rheumatic fever focuses on eliminating the streptococcal infection, managing symptoms, and preventing recurrence.

1. Antibiotics:

   • Penicillin G or V is the first-line treatment
   • Erythromycin for penicillin-allergic patients
   • Long-term antibiotic prophylaxis may be necessary

2. Anti-inflammatory drugs:

   • Aspirin for joint pain and inflammation
   • Corticosteroids for severe carditis

3. Supportive care:

   • Bed rest during the acute phase
   • Management of heart failure if present

4. Treatment of chorea:

   • Valproic acid or carbamazepine may be used for severe cases

Prevention

Prevention of rheumatic fever primarily involves prompt treatment of streptococcal throat infections. Key preventive measures include:

1. Early antibiotic treatment: Treating strep throat with antibiotics within 9 days of symptom onset can prevent rheumatic fever.

2. Antibiotic prophylaxis: For individuals with a history of rheumatic fever to prevent recurrence.

3. Improved living conditions: Reducing overcrowding and improving access to healthcare in high-risk populations.

4. Education: Raising awareness about the importance of treating strep throat and recognizing the signs of rheumatic fever.

Conclusion

Rheumatic fever remains a significant health concern, particularly in developing countries and among disadvantaged populations. While its incidence has decreased in many parts of the world due to improved living conditions and access to antibiotics, it continues to be a major cause of acquired heart disease in children globally.

Early recognition and treatment of streptococcal infections are crucial in preventing rheumatic fever. For those who develop the condition, prompt diagnosis and appropriate management can significantly reduce the risk of long-term complications, particularly rheumatic heart disease.

Ongoing research into the immunological mechanisms behind rheumatic fever may lead to new prevention strategies and treatments in the future. Until then, adherence to established guidelines for diagnosis, treatment, and prevention remains the best approach to managing this complex disease.

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