Chickenpox, Shingles (mechanism of diseases)

This is a flowchart on chickenpox and shingles, covering the etiology, pathophysiology, and manifestations.
ADDITIONAL TAGS:
Risk factors / SDOH
Cell / tissue damage
Structural factors
Chickenpox, Shingles
Medicine / iatrogenic
Infectious / microbial
Biochem / metabolic
Immunology / inflammation
Signs / symptoms
Tests / imaging / labs
Environmental, diet
Neoplasm / cancer
Flow physiology
Pathophysiology
Etiology
Manifestations
Varicella zoster virus (VZV), a human herpesvirus type 3
Airborne droplets
Direct skin contact with vesicle fluids
Transplacental
Transmission via…
Chickenpox: virus spreads from mucosal / epidermal lesions to regional lymphoid tissue → viremia
Virus remains dormant in dorsal root ganglia
Highly contagious infectivity; 2 days before to 5 days after exanthem onset
Age 12 years
Risk for severe VZV infection:
Immunosuppression
Pregnancy
Chronic skin / lung disease
Long term aspirin therapy
Infancy
↑ Reye syndrome
↑ complications (bacterial superinfection, pneumonia)
Incubation period: ~2 weeks, can range 10-21 days
Prodrome phase: 2-3 days, rare in children
Fever
Malaise
Headache
Muscle, joint pain
Lesions start as papules → superficial vesicles filled with clear fluid on erythematous base ("dewdrop on rose petal") → umbilicated and crusted → scab falls off, leaving depressed base → +/- postinflam pigmentation, +/- punched out scars (pockmarks)
Location: lesions start central (face, scalp trunk) → extremities. Affects oral and genital mucosa; spares palms and soles
Exanthem phase: Sequential eruptions of lesions, which are in multiple stages of evolution at once
Features of severe varicella:
Prolonged high fever (1 week)
Prolonged vesicle eruption (5 days)
Thrombocytopenia → hemorrhagic skin lesions
Visceral dissemination → encephalitis, pneumonia
Immunocompromise
Reactivation of VZV → replication in dorsal root ganglia
Virus travels through peripheral sensory nerves to the skin → shingles
Virus travels through local sensory nerves
HIV infection → AIDS
Immunosuppressive therapy
Malignancy
Decline in immune function with age
Risk factors for VZV reactivation:
Malnutrition
Chronic stress
In a dermatomal distribution, usually affecting 1-3 dermatomes on one side (commonly cervical, trigeminal, thoracic, lumbar):
Pain, may precede rash; "burning”, “throbbing”, or “stabbing”; +/- allodynia
Erythematous maculopapular rash → clear vesicles → pustulate, rupture after 3-4 days → crusting, involution on days 7-10
+/- fever, headache, fatigue, paresthesia, itching
Geniculate ganglion
Opthalmic of CN-5
Reactivation in…
Herpes zoster oticus (Ramsay Hunt): Skin symptoms in auditory canal, ear; vertigo, SNHL, ipsilateral facial paralysis
Herpes zoster ophthalmicus: conjunctivitis, keratitis, intraocular infxn; +/- glaucoma, blindness

[@cheetahgoldenfire]

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[@yasmeenrashid7654]

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