Complications of Chickenpox (Varicella)

1. Skin / Bacterial Superinfection (Most Common)

• Secondary bacterial infection of excoriated (scratched) skin lesions - most often by Staphylococci or Streptococci
• Can produce: impetigo, cellulitis, erysipelas, and rarely necrotizing fasciitis
• Local infections can lead to scarring, and rarely septicemia and metastatic infection
• Bullous lesions may develop when vesicles are superinfected by Staphylococci producing exfoliative toxins
• Varicella is strongly associated with invasive Group A Streptococcal (GAS) infections - usually within 2 weeks of rash onset and potentially very virulent; in the prevaccine era, 15-30% of invasive GAS hospitalizations were linked to varicella

2. Respiratory - Varicella Pneumonia

• Most serious complication in adults
• Features: cough, dyspnea, tachypnea, high fever, pleuritic chest pain, cyanosis, hemoptysis - beginning 1-6 days after rash onset
• Symptoms often exceed physical findings; imaging shows diffuse peribronchial nodular densities, concentrated perihilar and at bases
• Mortality: 10-30% in adults with frank pneumonia (less than 10% if immunocompetent patients receive prompt antiviral therapy)

3. Central Nervous System (CNS) Complications

• Aspirin must be avoided in children with varicella because it predisposes to Reye syndrome (acute encephalopathy with fatty degeneration of the liver)
• VZV antigens, antibodies, and DNA can be detected in CSF, suggesting direct CNS infection

4. Complications in Pregnancy (Maternal + Fetal)

• Increased risk of severe varicella pneumonia and disseminated infection - can be fatal
• Premature labor

• Congenital Varicella Syndrome (CVS): occurs in ~1% when maternal infection is in first 20 weeks (highest risk 2% between 13-20 weeks)
  • Features: limb hypoplasia, skin scarring (cicatricial), ocular abnormalities, CNS defects, autonomic dysfunction
• Perinatal varicella (within 10 days of birth) is much more serious than infection even a few weeks later - neonates can develop life-threatening disseminated disease

5. Complications in Immunocompromised Patients

• Markedly increased morbidity and mortality
• Continued viral replication leads to: prolonged high-level viremia, more extensive rash, hemorrhagic or purpuric lesions, prolonged vesicle formation
• Visceral dissemination: involves lungs, liver, brain, adrenal glands
• Severe abdominal and back pain are common prodromal symptoms in this group
• Clinical hepatitis (rare in immunocompetent) is a significant complication here

6. Hepatitis

• Mildly elevated aminotransferases are common during varicella in general
• Clinical hepatitis is rare in immunocompetent patients but significant in immunocompromised

7. Ophthalmic Complications

• Keratitis
• Iritis (uveitis)
• Optic neuritis

8. Other Rare Complications

• Myocarditis
• Glomerulonephritis
• Orchitis
• Pancreatitis
• Gastritis and ulcerative lesions of the bowel
• Arthritis
• Henoch-Schönlein vasculitis (small vessel vasculitis / IgA vasculitis)

Summary by Risk Group

Key Clinical Notes

• Do NOT give aspirin to patients with varicella (risk of Reye syndrome)
• Acyclovir is recommended for adolescents, adults, immunocompromised patients, and those on steroids - ideally within 24 hours of rash onset
• Varicella vaccination has dramatically reduced hospitalizations and the rate of invasive Group A Streptococcal infections associated with varicella