Successful differentiation of herpes zoster‐associated erythema multiforme from generalized extension of herpes by rapid polymerase chain reaction analysis

<jats:title>Abstract</jats:title><jats:p>The polymerase chain reaction (<jats:styled-content style="fixed-case">PCR</jats:styled-content>) assay for varicella zoster virus (<jats:styled-content style="fixed-case">VZV</jats:styled-content>), herpes simplex virus (<jats:styled-content style="fixed-case">HSV</jats:styled-content>)‐1 and <jats:styled-content style="fixed-case">HSV</jats:styled-content>‐2 is available for use. Sometimes the differential diagnosis of the generalized herpes zoster (<jats:styled-content style="fixed-case">HZ</jats:styled-content>), <jats:styled-content style="fixed-case">HSV</jats:styled-content>1/2, and drug eruption is difficult. We report a case of <jats:styled-content style="fixed-case">HZ</jats:styled-content> followed by the vesicular erythema multiforme (<jats:styled-content style="fixed-case">EM</jats:styled-content>)‐like lesion. In this case the use of <jats:styled-content style="fixed-case">PCR</jats:styled-content> was of great assistance. A 78‐year‐old Japanese man without any significant previous history of disease was admitted to our hospital complaining of zosteriform vesicle on an erythematous base from his right shoulder to the upper arm. We diagnosed him with <jats:styled-content style="fixed-case">HZ</jats:styled-content> at the level of right Th2. In spite of the prompt start of antiviral therapy, a secondary new vesiculous erythema developed on his trunk. Clinically, it was quite difficult to differentiate the lesion from the generalized <jats:styled-content style="fixed-case">HZ</jats:styled-content>. Rapid <jats:styled-content style="fixed-case">PCR</jats:styled-content> assay of effusion and crust for <jats:styled-content style="fixed-case">VZV</jats:styled-content> was performed. A <jats:styled-content style="fixed-case">PCR</jats:styled-content> assay of <jats:styled-content style="fixed-case">VZV</jats:styled-content> was positive for the crust taken from the primary lesion, while it was negative for the effusion and crust of the secondary widespread lesion. We diagnosed the secondary widespread lesion as an <jats:styled-content style="fixed-case">EM</jats:styled-content>‐type drug eruption induced by acyclovir, or an <jats:styled-content style="fixed-case">EM</jats:styled-content> associated with herpes zoster. We then stopped the use of acyclovir and applied steroid ointment of a very strong class for the secondary lesions, which improved after a few days. A <jats:styled-content style="fixed-case">PCR</jats:styled-content> assay for <jats:styled-content style="fixed-case">VZV</jats:styled-content> was useful for ruling out the generalized <jats:styled-content style="fixed-case">HZ</jats:styled-content> in our case with secondary developed vesiculous lesions.</jats:p>