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Skin infections

Viral case challenge

A 21-year old student is studying for exams. He presents with fever, cervical lymphadenopathy and a facial rash, which has been present for 3 days.

Facial rash

Which terms best describe the rash on his face? * Necrotic papules *! Umbilicated vesicles * Fissured plaques * Crusted pustules Explanation: The image shows innumerable clusters of umbilicated vesicles. 'Umbilicated' refers to central dimples in each lesion.

He also has an itchy rash behind his knees, which has recurred since childhood.

Popliteal fossa rash

What terms best describe the rash in the popliteal fossa #! Lichenification || Thickened skin with increased skin markings #! Plaque || A palpable flat lesion greater than 0.5cm diameter. # Vesicles # Pustules What is the diagnosis of this rash? * Molluscum contagiosum *! Atopic dermatitis * Scabies * Tinea corporis Explanation: The itchy rash in the popliteal fossae is atopic dermatitis.

Facial rash

The likely diagnosis of the rash on his face is: * Severe hand foot and mouth infection * Varicella infection *! Eczema herpeticum * Smallpox Explanation: He has been recently infected with _herpes simplex_, which may cause a severe eruption in those with atopic dermatitis, known as eczema herpeticum. How might you confirm the presence of herpes simplex virus? #! Viral culture # Swab for microscopy and bacterial culture #! PCR #! Tzanck smear What treatment would you prescribe? #! Topical steroid to popliteal fossa #! Acyclovir 800mg three times a day # Acyclovir 100mg five times a day # Penciclovir four times daily Explanation: A moderate potency topical steroid and emollients should be prescribed for a couple of weeks to treat the active atopic dermatitis in the flexures. Explanation: Oral acyclovir has good bioavailability so intravenous acyclovir is only necessary in patients unable to swallow. The standard dose of acyclovir for recurrent herpes simplex infections is 200mg five times daily, but in severe infections the dose should be increased to that normally used for herpes zoster i.e. 800mg five times daily. The medication should be continued until the vesicles have cleared, generally within 5 to 10 days. Eczema herpeticum may rarely recur. Explanation: Penciclovir is a topical antiviral and would be unlikely to have much impact on herpes infections of this extent.