A 9-year-old girl with a Rash on Face

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.

Here is Her Story:

Initial Exposure to HSV-1
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The virus enters through microabrasions on the left cheek
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Local viral replication in epithelial cells (leading to cell lysis and inflammation.)
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Lysis of infected cells causes a fluid-filled vesicle on the red, inflamed skin. This corresponds to the round plaque on erythematous base observed on the left cheek.
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As the immune system responds, the vesicles may rupture, forming crusts. Satellite vesicles may appear as the virus spreads locally within the skin.
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Recruitment of immune cells (lymphocytes, neutrophils) to the site of infection.
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This leads to the ipsilateral cervical lymphadenopathy as nearby lymph nodes react to the viral presence.
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Cytokines and other immune mediators enter the bloodstream, leading to systemic symptoms like fever (4-day history).
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The fever occurs as part of the body’s effort to fight off the viral infection.
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The infection is localized to the skin, with no viral spread to mucosal surfaces, explaining the absence of mucosal lesions.
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After the acute infection resolves, the virus migrates to the trigeminal ganglia where it remains dormant.
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Under certain conditions (stress, immune suppression), the virus may reactivate, causing recurrent lesions in the same area.

Image Sources: NEJM,

Why Other Options Are Wrong:

A) Cutaneous non-tuberculous mycobacterial infection:

• Wrong: Typically presents with chronic, non-healing nodules or ulcers. No vesicles or rapid onset fever.

B) Impetigo:

• Wrong: Presents with honey-colored crusts, not vesicles or lymphadenopathy. Fever is uncommon.

D) Syphilitic chancre:

• Wrong: Painless ulcer without vesicles or fever, and develops over weeks, not days.

E) Tinea corporis:

• Wrong: Fungal infection presents as scaly, ring-shaped lesions without vesicles or fever.

Stay Hungry, Stay Curious!

Dr. Shoaib Ahmad