A 27-year-old man presented with a rash that was not painful or pruritic. During a haircut 4 days prior, clippers nicked the back of his neck. The first lesions appeared at this site. The rash then spread over the back of his neck and side of his face. Oral clindamycin, started 1 day prior, had not led to improvement. He did not have vision or hearing changes.

On examination, the patient was not in distress, and his vital signs were normal. A bullous, nonerythematous rash was present on his neck and face (Figure 1). The bullae were approximately 1 to 1.5 cm in diameter.

QUESTION

Based on the patient's history and physical examination, which one of the following is the most likely diagnosis?

• A. Bullous pemphigoid.

• B. Cutaneous anthrax.

• C. Herpes zoster.

• D. Primary herpes simplex virus infection.

DISCUSSION

The answer is D: primary herpes simplex virus (HSV) infection. HSV is a double-stranded DNA virus that enters the body through mucous membranes or damaged skin. An estimated 62% of adults in the United States are infected with HSV.¹ When infected cells die, they release fluid intradermally, creating large vesicles filled with clear fluid. The vesicles typically occur on the oral mucous membranes or in the genital area. This patient was probably infected when the clippers nicked his skin. In primary infections, patients may also have fever, malaise, headache, and local lymphadenopathy. Without treatment, lesions resolve after 7 to 18 days.¹