What are the clinical features and management of chicken pox?

Clinical Features and Management of Chicken Pox

Chicken pox (varicella) is characterized by a rapidly evolving vesicular rash that appears first on the head, then trunk, and finally extremities, with new vesicle formation continuing for 2-4 days, accompanied by fever, pruritus, headache, malaise, and anorexia. 1

Clinical Features

Rash Characteristics

• Evolution pattern: The rash evolves through stages of macules, papules, vesicles, pustules, and crusts
• Distinctive feature: Unlike monkeypox or smallpox, chicken pox lesions appear in successive crops, with lesions in different stages present simultaneously 2
• Distribution: Begins on head, progresses to trunk, then extremities 1
• Duration: New vesicle formation typically continues for 2-4 days 1
• Density: Uncomplicated severe cases may have more than 1000 lesions 3

Associated Symptoms

• Fever (typically low-grade)
• Pruritus (often intense)
• Headache
• Malaise
• Anorexia 1

Special Populations

• Children: Generally mild to moderate illness 3
• Adults: Severity increases with age; adults tend to have more severe disease 4
• Secondary household cases: Often more severe than the primary case 4
• Immunocompromised patients: Potentially fatal; requires immediate treatment 4

Complications

Common Complications

• Secondary bacterial skin infections
• Scarring

Severe Complications

• Visceral dissemination: Especially VZV pneumonitis 1
• Central nervous system involvement: Encephalitis, cerebellar ataxia
• Secondary bacterial infections: Cellulitis, necrotizing fasciitis, sepsis
• Pneumonia: More common in adults and immunocompromised patients
• Death: Rare in immunocompetent children but higher risk in adults and immunocompromised individuals 1, 3

Management

Supportive Care

• Antipyretics for fever (avoid aspirin due to risk of Reye syndrome)
• Antihistamines for pruritus
• Proper skin hygiene to prevent secondary infections
• Adequate hydration

Antiviral Therapy

Indications for acyclovir treatment:

• Immunocompromised patients (immediate IV treatment) 4
• Secondary and tertiary cases in a family
• Adolescents and adults with chickenpox
• Treatment initiated within 24 hours of rash onset is most effective 5, 4

Dosing:

• Children: 10-20 mg/kg orally 4 times daily for 5-7 days
• Adults: 800 mg orally 4 times daily for 5 days 5

Benefits of antiviral therapy:

• Reduces duration of fever
• Decreases constitutional illness
• Shortens time to cutaneous healing 4

Isolation Precautions

• Isolate patients until all lesions have crusted (typically 5-7 days after rash onset)
• Avoid contact with susceptible individuals, especially:
  • Pregnant women
  • Immunocompromised individuals
  • Infants

Prevention

Vaccination

• Live attenuated varicella vaccine is recommended for routine childhood immunization 6
• Efficacy: 80-85% effective against all disease, >95% effective against severe disease 3
• Schedule: Two-dose strategy recommended 7
• Impact: Significant reduction in disease incidence, complications, hospitalizations, and deaths where implemented 3

Post-exposure Prophylaxis

• Varicella-zoster immune globulin (VZIG) is indicated for susceptible high-risk patients exposed to varicella 6

Special Considerations

Herpes Zoster (Shingles)

• Reactivation of latent VZV from dorsal root ganglia 6
• Risk increases with age or immunosuppression 1
• Characterized by painful vesicular rash in a dermatomal distribution 1
• Prevention through zoster vaccination is recommended for adults ≥50 years 8

Pregnancy

• Pregnant women without immunity are at risk for severe disease
• Risk of congenital varicella syndrome if infection occurs during first 20 weeks of pregnancy
• VZIG should be considered for susceptible pregnant women exposed to varicella 6

Common Pitfalls in Management

• Delayed treatment: Antiviral therapy should be initiated within 24 hours of rash onset for maximum effectiveness
• Misdiagnosis: Chicken pox can be confused with other vesicular rashes (smallpox, monkeypox, disseminated herpes simplex)
• Inappropriate use of antibiotics: Unless secondary bacterial infection is present
• Use of aspirin: Avoid in children due to risk of Reye syndrome
• Inadequate isolation: Patients remain contagious until all lesions have crusted

By recognizing the characteristic features and implementing appropriate management strategies, the morbidity and mortality associated with chicken pox can be significantly reduced.