Question

A 9-year-old girl presented to the dermatology department with a 7-day history of a lesion on the left cheek and a 4-day history of fever. On physical examination, a round plaque 3 cm in diameter on an erythematous base was observed on the patient’s left cheek, with overlying crusting and a single intact vesicle. Satellite vesicles and ipsilateral cervical lymphadenopathy were also present. There were no mucosal lesions.

What is the most likely diagnosis?

A) Cutaneous non-tuberculous mycobacterial infection

B) Impetigo

C) Primary cutaneous HSV-1 infection

D) Syphilitic chancre

E) Tinea corporis

C) Primary cutaneous HSV-1 infection:

Correct: Vesicles on an erythematous base, fever, lymphadenopathy, and crusting match HSV-1 presentation.

Initial Exposure: HSV-1 Contact (e.g., infected saliva or skin)
⬇️
Viral Entry into Skin/Epidermis
⬇️
🧠 Key Insight: Virus infects keratinocytes
⬇️
Viral Replication in Epidermal Cells
⬇️
🧠 Key Insight: Vesicles form due to cell lysis → blistering
⬇️
Inflammatory Response Triggered
⬇️
Erythema + Swelling (due to local cytokine release ↑)
⬇️
🧠 Key Insight: Vesicles rupture → Crusting of Lesions
⬇️
Virus Spreads Locally → Satellite Vesicles
⬇️
Systemic Spread → Fever & Ipsilateral Cervical Lymphadenopathy
⬇️
🧠 Key Insight: Immune Response Activation (Fever, Lymph nodes swell)

Why Other Options Are Incorrect:

Cutaneous non-tuberculous mycobacterial infection
🧠 Key Insight:

• Slow Progression (weeks to months) ⬇️

• No Vesicles or Crusting ⬇️

• No Rapid Inflammatory Response

⬇️

Impetigo (Bacterial Infection)
🧠 Key Insight:

• Honey-colored crusts (not vesicles with crusts)

• Mostly painless and superficial ⬇️

• No Lymphadenopathy

⬇️

Syphilitic Chancre
🧠 Key Insight:

• Painless Ulcer, No Vesicles ⬇️

• No Fever, Lymphadenopathy typically later

• Uncommon in children

⬇️

Tinea Corporis (Fungal)
🧠 Key Insight:

• Ring-shaped lesion, Scaly, No Vesicles

• No Crusting or Fever

  

Flashcards

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