Chickenpox (Varicella) — Lesion Description

Causative Agent

Distribution

• Begins on the face and scalp, then spreads rapidly to the trunk (centripetal distribution)
• Relative sparing of the extremities
• Denser on the back between the shoulder blades; more profuse on medial limb aspects
• Mucous membranes are also involved — mouth, nose, pharynx, vagina (vesicles rupture quickly, leaving shallow 2–3 mm ulcers)
• Lesions appear in successive crops over several days

Sequential Morphological Stages

The hallmark diagnostic feature: all stages present simultaneously in any one area of skin ("pleomorphic" or "crops at different stages"). This distinguishes varicella from smallpox, where all lesions are at the same stage.

Key Vesicle Characteristics

• Size: 2–3 mm in diameter
• Shape: Elliptical, with long axis parallel to skin fold lines
• Wall: Superficial and thin-walled
• Surrounding halo: Irregular zone of erythema — gives the "dewdrop on a rose petal" appearance
• Evolution: Vesicle → cloudy pustule (influx of inflammatory cells) → umbilicated → crust
• Average count: 250–500 lesions in healthy children; more numerous in adults and immunocompromised

Healing & Scarring

• Crusts fall off spontaneously in 1–3 weeks, leaving shallow pink depressions that fade
• Scarring is rare unless lesions are scratched or superinfected
• May leave hypopigmented macules persisting weeks to months
• If scars occur, they are depressed and poxlike

In Immunocompromised Patients

• Lesions may lack surrounding erythema
• Vesicles may not progress to pustules
• Larger vesicles that may fuse (as seen in panel F below)
• Higher risk of disseminated/hemorrhagic varicella

Clinical Images

A–B: Typical varicella in children — lesions in all stages simultaneously. C: Early vesicles with erythematous halo ("dewdrop on a rose petal"). D: Crusted lesions on day 3. E: Large umbilicated pustules in adult with severe varicella and pneumonia. F: Immunocompromised patient — fused vesicles without erythema or progression to pustules.

Crops of small erythematous papules with central vesiculation and crust formation in various stages.

Associated Symptoms

• Pruritus — the most distressing symptom, present until all lesions crust
• Fever — proportional to rash severity; persists while new lesions appear (up to 40.5°C in severe cases)
• Prodrome in older children/adults: 2–3 days of fever, malaise, headache, anorexia, backache