Diagnosis

Chickenpox

Etiology

Cause [ewv]

• Chickenpox is caused by varicella zoster virus

•  A highly contagious airborne disease spread by inhalation of airborne respiratory droplets (coughing, sneezing) or direct contact with vesicles

• Average incubation period: 2 weeks

Pathophysiology [t9o][ewv]

1. Inhalation of contaminated respiratory droplets

2. Infection of the conjunctivae or the mucosae of the upper respiratory tract

3. Viral proliferation occurs in regional lymph nodes

4. Primary viremia initiates the production of IgG, IgM, and IgA

5. IgG antibodies persist for lifelong cell-mediated immune responses

6. Probably spread from mucosal and epidermal lesions to local sensory nerves

7. VZV then remains latent in the dorsal ganglion cells of the sensory nerves

8. Reactivation of VZV --> herpes zoster (shingles)

Risk factors [ewv]

• Immunocompromised (cancer, chemotherapy, HIV, immunodeficiency disorders)

• Pregnant women

Complications [ewv]

• Varicella pneumonia

• CNS: Meningitis/encephalitis, acute cerebellar ataxia, Guillain-Barré syndrome

• Reye syndrome (encephalitis and fatty liver): aspirin to children with varicella

• Bacterial superinfection of cutaneous lesions: cellulitis, impetigo, or erysipelas

• Septicemia

• Congenital varicella syndrome

  • Primary maternal chickenpox infection in early to mid-pregnancy

  • Limb hypoplasia, muscular atrophy, skin scarring, cortical atrophy, microcephaly, cataract formation, and rudimentary digits

• Other: Thrombocytopenia, hepatitis, glomerulonephritis, optic neuritis, keratitis, arthritis, myocarditis, pancreatitis, orchitis, and vasculitis

Epidemiology

Incidence per 100.000 [eyn][n6b][zss][qd1]

Approach

• Clinical presentation: generalized skin rash of itchy blisters accompanied by fever, fatigue, pharyngitis, and headaches, usually lasting 5 to 7 days

• Vesicular fluid culture

• Vesicular fluid: polymerase chain reaction

• Biopsy with immunofluorescence

Treatment

1. Benign disease that requires symptomatic therapy only: [ewv][t9o]

   • Pruritus: calamine lotion, pramoxine gel, powdered oatmeal baths, antihistamine

2. Severe varicella infection: 

   • Oral acyclovir started within 24 to 48 hours of rash onset

3. Immunosuppressed or immunocompromised:

   • Intravenous acyclovir

   • Varicella-zoster immune globulin: 125 U/10 kg, maximum 625 U

   • VZV Vaccination

Differential diagnoses

Bullous pemphigoid, Cellulitis, Coxsackievirus infection, Dermatitis herpetiformis, Drug eruptions, Eczema, Erysipelas, Erythema multiforme, Herpes simplex, Herpes zoster, Impetigo, Insect Bite, Mpox, Pemphigus vulgaris, Pityriasis lichenoides, Rickettsia, Scabies, Smallpox, Syphilis