Herpes zoster following intra-articular corticosteroid injection.

Localized herpes zoster following intra-articular corticosteroid injection is remarkable. We describe an 80-year-old woman with severe osteoarthritis that received an intra-articular injection of 80 mg methylprednisolone in her knee, followed 1 day later by the appearance of linear unilateral vesicles and bullae on her leg in a dermatomal distribution adjacent to the injection site. The roofs of several blisters showed classic viral cytopathic effects for herpes including keratinocytes with multinucleation and margination of chromatin. Varicella zoster virus immunostaining revealed positive staining in the keratinocytes. One plausible explanation is herpes zoster virus reactivation secondary to localized immunosuppression from corticosteroid injection.