Rheumatic Fever caused by Group A Streptococcus (GAS) aka. Streptococcus pyogenes: ไข้ ข้อ คอ คา คิว ผิวแดง Diagnosis by Jones Criteria

Introduction

Rheumatic fever is a systemic inflammatory disease that arises as a complication of untreated or inadequately treated Group A β-hemolytic streptococcal (GAS) pharyngitis. It predominantly affects children aged 5 to 15 but has lifelong implications, especially due to its potential to cause rheumatic heart disease (RHD), a major cause of cardiovascular morbidity and mortality worldwide. This article will delve into the pathophysiology, clinical manifestations, diagnostic criteria, and management of rheumatic fever, providing a deep understanding of this disease for internal medicine practitioners.

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Pathophysiology of Rheumatic Fever

Rheumatic fever results from an autoimmune response triggered by a Group A Streptococcus (GAS) infection, commonly in the form of pharyngitis. The underlying mechanism involves molecular mimicry, where the body's immune system, in attempting to fight off the bacterial infection, produces antibodies that cross-react with human tissues, particularly in the heart, joints, skin, and central nervous system. Key bacterial antigens, such as the M protein on the streptococcal cell wall, share structural similarity with human tissues, leading to an autoimmune attack on the body.

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Clinical Manifestations: The Mnemonic “ไข้ ข้อ คอ คา คิว ผิวแดง” (Fever, Joints, Chorea, Carditis, Nodules, Erythema)

1. Fever (ไข้)

• Minor Criterion: Fever is often low-grade and persistent, signaling systemic inflammation. It is a minor criterion in the diagnosis but crucial for recognizing the systemic inflammatory response in rheumatic fever.

2. Migratory Polyarthritis (ข้อ)

• Major Criterion: Arthritis in rheumatic fever typically affects large joints, such as the knees, ankles, elbows, and wrists. The inflammation is “migratory,” moving from one joint to another within a few days. Affected joints are red, swollen, warm, and painful, but the arthritis resolves without permanent damage.

3. Sydenham’s Chorea (คอ)

• Major Criterion: Sydenham’s chorea is characterized by involuntary, jerky movements that primarily affect the face, hands, and feet. The condition, also known as St. Vitus' dance, includes muscle weakness and emotional instability. It can occur months after the initial streptococcal infection, making it a delayed manifestation of rheumatic fever.

4. Carditis (คา)

• Major Criterion: Carditis is the most severe manifestation of rheumatic fever, affecting all layers of the heart (pancarditis), including the endocardium, myocardium, and pericardium. Clinical findings may include:
  • New heart murmurs due to valvular involvement (primarily mitral and aortic valves).
  • Signs of heart failure such as dyspnea, fatigue, and edema.
  • Pericardial friction rub or effusion, detected via auscultation and imaging.
• Long-term, carditis may result in rheumatic heart disease (RHD), which often leads to mitral valve stenosis and can severely impact cardiac function.

5. Subcutaneous Nodules (คิว)

• Major Criterion: These are small, firm, and painless nodules under the skin, often located over bony prominences or tendons (elbows, wrists, knees, and Achilles tendon). Although painless, their presence is significant for diagnosis.

6. Erythema Marginatum (ผิวแดง)

• Major Criterion: This rash is characteristic of rheumatic fever and consists of pink or red macules that spread outward with a clear center, forming a ring-like appearance. The rash is non-pruritic and primarily affects the trunk and proximal limbs.

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Diagnosis of Rheumatic Fever: The Jones Criteria

The Jones Criteria help diagnose rheumatic fever, requiring a combination of major and minor criteria along with evidence of a recent streptococcal infection. The criteria include:

• Major Criteria:
  1. Migratory polyarthritis
  2. Carditis
  3. Sydenham’s chorea
  4. Subcutaneous nodules
  5. Erythema marginatum
• Minor Criteria:
  1. Fever
  2. Arthralgia
  3. Elevated acute-phase reactants (ESR, CRP)
  4. Prolonged PR interval on ECG

Diagnosis: To confirm a diagnosis of rheumatic fever, the following combinations are necessary:

• 2 major criteria, or
• 1 major and 2 minor criteria

In both cases, the diagnosis requires supporting evidence of a recent Group A Streptococcus infection (e.g., positive throat culture, elevated ASO titers, or anti-DNase B titers).

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Laboratory Findings and Imaging

• Throat Culture: Detects the presence of Group A Streptococcus.
• ASO Titer: Elevated anti-streptolysin O (ASO) titers are a marker of recent streptococcal infection.
• CRP and ESR: Elevated levels indicate systemic inflammation.
• ECG: Prolonged PR interval can be present in cases with carditis.
• Echocardiogram: Helps detect valvular lesions, chamber enlargement, and pericardial effusion.

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Management of Rheumatic Fever

1. Antibiotic Therapy

Goal: Eradicate any residual Group A Streptococcus (GAS) infection to prevent recurrence of rheumatic fever.

• First-line Treatment:
  • Benzathine Penicillin G (IM):
    • Dosage: 1.2 million units intramuscularly (IM) as a single dose for adults and children weighing more than 27 kg.
    • For children under 27 kg, the dose is 600,000 units IM as a single dose.
  • Penicillin V (oral):
    • Dosage: 250 mg taken orally 2-3 times per day for 10 days.
• For Penicillin-Allergic Patients:
  • Erythromycin:
    • Dosage: 250 mg taken orally 2-3 times per day for 10 days.

2. Anti-inflammatory Treatment

Objective: Reduce inflammation, relieve pain, and control symptoms of arthritis and carditis.

• Aspirin (for arthritis and other inflammatory symptoms):
  • Dosage for Adults: 75-100 mg/kg per day divided into 4 doses.
  • Example Regimen: For a 70 kg adult, this would be approximately 5,250-7,000 mg per day, divided as 1,300-1,750 mg per dose, four times daily.
  • Continue treatment until symptoms resolve, then taper off gradually over 1-2 weeks.
• Corticosteroids (for severe carditis or heart failure symptoms):
  • Prednisone:
    • Dosage: 1-2 mg/kg per day, divided into two doses.
    • Taper slowly over 2-4 weeks after significant improvement in symptoms.
    • Example: For a 70 kg patient, this would be approximately 70-140 mg daily, divided into two doses.

3. Symptomatic Management

Objective: Address specific symptoms associated with severe manifestations of rheumatic fever, including heart failure and chorea.

• Heart Failure (due to significant carditis):
  • Diuretics:
    • Furosemide: 20-40 mg orally, once or twice daily, depending on the degree of fluid overload. Adjust as needed based on patient response and kidney function.
  • ACE Inhibitors (if there is left ventricular dysfunction):
    • Enalapril: Start with 2.5-5 mg orally, once daily, and adjust to a target dose of 10-20 mg once daily, depending on blood pressure and renal function.
  • Beta-blockers may also be used in specific cases, but they should be initiated with caution.
• Chorea (for severe involuntary movements):
  • Haloperidol:
    • Dosage: 0.5-1 mg orally, 2-3 times per day, titrated based on response. The dose can be gradually increased up to a maximum of 5 mg daily.
  • Alternatively, Valproic Acid may be considered:
    • Dosage: 10-15 mg/kg per day, divided into two doses, and titrated as needed. Target levels should be monitored due to potential side effects.

4. Long-term Secondary Prophylaxis

Patients with a history of rheumatic fever are at a high risk of recurrence, particularly if they had carditis. Long-term antibiotic prophylaxis with benzathine penicillin G is used to prevent recurrent streptococcal infections, which can worsen heart disease. The duration and frequency of prophylaxis depend on the patient’s history and presence of cardiac involvement.

• Benzathine Penicillin G (IM):
  • Dosage: 1.2 million units intramuscularly every 3-4 weeks for adults and children over 27 kg.
  • For children under 27 kg, the dose is 600,000 units IM every 3-4 weeks.

Duration of Prophylaxis:

• Without Carditis: Continue prophylaxis for at least 5 years or until the patient reaches age 21, whichever is longer.
• With Carditis but No Residual Heart Disease: Continue for at least 10 years or until age 21, whichever is longer.
• With Carditis and Persistent Valvular Disease: Continue until age 40 or for life, depending on the severity of valvular involvement.

Summary of Dosages for Common Medications in Rheumatic Fever Management

This detailed management approach, with drug dosages and treatment regimens, ensures comprehensive care for patients with rheumatic fever and reduces the risk of complications and recurrence.

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Complications: Rheumatic Heart Disease (RHD)

The most significant long-term consequence of rheumatic fever is rheumatic heart disease (RHD), characterized by chronic and progressive valve damage, especially of the mitral and aortic valves. Complications of RHD include:

1. Mitral Valve Stenosis: The most common valvular issue, leading to left atrial enlargement, pulmonary hypertension, and ultimately heart failure.
2. Aortic Valve Disease: Can lead to both aortic stenosis and aortic regurgitation.
3. Heart Failure: Progressive valvular disease impairs cardiac output, leading to congestive heart failure.
4. Atrial Fibrillation: Valve deformities and left atrial enlargement predispose patients to atrial fibrillation, increasing the risk of thromboembolic events.

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Prevention

1. Prompt Treatment of Streptococcal Pharyngitis: Early treatment of streptococcal sore throat with antibiotics is the primary method to prevent rheumatic fever.
2. Secondary Prophylaxis: Regular prophylactic antibiotics in individuals with a history of rheumatic fever to prevent recurrence and further heart damage.

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Conclusion

Rheumatic fever remains a global health challenge, especially in low-resource settings. Early recognition and treatment of GAS pharyngitis, coupled with appropriate management of rheumatic fever, can prevent serious complications like rheumatic heart disease. Internal medicine physicians play a crucial role in diagnosing and managing rheumatic fever, implementing long-term prophylaxis, and educating patients about the importance of adherence to prevent recurrence. By understanding the intricate details of this disease, clinicians can significantly reduce its long-term impact on patients’ lives and contribute to improving global cardiovascular health.