Viral infection in a child: Chickenpox Flashcards

1
Q

Define chickenpox.

A

Contagious infectious disease caused by the DNA herpes virus varicella zoster.

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2
Q

Explain the aetiology of antenatal chickenpox.

A

Varicella embryopathy (VE) is caused by transplacental transmission during maternal infection in 2.2% of foetuses if < 20 weeks’ gestation.

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3
Q

Explain the aetiology of perinatal chickenpox.

A

Varicella of the newborn (VON); severity depends on the time of maternal infection:

  • 21-5 days before delivery: VON appears in first 4 days and there is a good prognosis.
  • 5 days before delivery or 2 days after delivery: VON presents day 6-26; may be mild or severe (30% mortality).
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4
Q

Explain the aetiology of postnatal chickenpox.

A

Transmission via the respiratory route; preterm infants are at higher risk due to lack of placental varicella IgG transfer in the third trimester.

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5
Q

Explain the aetiology of childhood chickenpox.

A

Virus enters the respiratory tract and undergoes replication in the regional lymph nodes. At 4-6 days a primary viraemia spreads the virus to the reticuloendothelial cells primarily in the spleen and liver. At 11-24 days there is a secondary viraemia to the viscera and skin, which elicits typical skin lesions.

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6
Q

What are risk factors for chickenpox?

A

Maternal

Family contact

School contact with infected individuals

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7
Q

Summarise the epidemiology of chickenpox.

A

15% of pregnant women are susceptible to varicella infection.

Incidence of varicella during pregnancy is 3/1000 in the UK. Household transmission rates are 80-90%.

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8
Q

What are signs and symptoms of varicella embryopathy?

A

CNS: Microcephaly, paralysis, developmental delay, seizures.

Ocular: Cataracts, chorioretinitis, microphthalmia, nystagmus.

Musculoskeletal: Cicatricial dermatomal skin lesions and scarring, unilateral atrophy of a limb with scarring and paresis, rudimentary digits.

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9
Q

What are signs and symptoms of varicella of the newborn?

A
  • Prodrome: Poor feeding, mild pyrexia and malaise.
  • Rash: Morbiliform rash in the prodrome develops into a generalized pruritic vesicular rash.
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10
Q

What are signs and symptoms of childhood chickenpox?

A

Prodrome: Mild pyrexia precedes skin manifestation by 1-2 days.

Rash: Appears in crops at different stages (papule, vesicle, pustule and crust). Varicella’s hallmark is the simultaneous presence of different stages of skin lesions and intense pruritus.

Systemic: Abdominal pain, headache, malaise, anorexia, cough, coryza, sore throat.

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11
Q

What are appropriate investigations for chickenpox?

A

Varicella infection is usually a clinical diagnosis.

Specific test: Serology (varicella-specific IgM) in fetal blood, detection of varicella antigens by ELISA, virology from vesicular fluid.

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12
Q

What is the management of chickenpox?

A

Conservative: Cool compresses, calamine lotion, regular bathing to manage pruritus, discourage scratching to prevent scarring (mittens may be necessary).

Medical: Sedating antihistamines for pruritus, acyclovir is indicated for moderate to severe disease.

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13
Q

When is varicella Ig indicated?

A

Infants born to mothers with infection 5 days before delivery or 2 days after.

At-risk infants (<28 weeks or < 1000 grams).

Exposed seronegative pregnant women.

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14
Q

How is chickenpox prevented?

A

Routine VZ immunisation is available in some countries (USA, Canada, Germany, Australia, Uruguay).

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15
Q

What are complications associated with chickenpox?

A

In childhood varicella 1/50 cases are associated with complications.

Neurological: Meningoencephalitis, encephalitis, acute cerebellar ataxia, Reye syndrome.

Skin: Impetigo (most common complication), scarring, necrotising fasciitis.

Other: Pneumonia, GN, myocarditis, pancreatitis, HSP.

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16
Q

What is the prognosis of chickenpox?

A

In otherwise healthy children aged 1–14 years, mortality rate is 2/100,000 cases. Patients with previous VE have a higher incidence of VZ in the first 10 years of life.