Refractory Post-Zoster Eosinophilic Dermatitis of the Eyelids Successfully Treated With Mycophenolate Mofetil

Post-zoster eosinophilic dermatitis is a rare skin disease caused by the infiltration of eosinophils into the dermis at the site of healed herpes zoster lesions. Since its initial report by Mitsuhashi and colleagues in 1997, there have been only 11 documented cases, predominantly among Asian patients. Most cases can be treated effectively with topical corticosteroids. We report a case of post-zoster eosinophilic dermatitis with a peculiar clinical manifestation and refractory course. A Japanese woman in her 40s presented with persistent pain and swelling of the right eyelid after treatment for herpes zoster in the right ophthalmic nerve. Histologically, the diffuse inflammatory infiltration of lymphocytes and eosinophils was noted in the entire dermis. Despite various treatments in addition to prednisolone, the symptoms did not improve for approximately 1 year. Eventually, systemic corticosteroid in addition to mycophenolate mofetil induced remission. This is first report of this combination for the treatment of post-zoster eosinophilic dermatitis. This case underscores the need for systemic therapy to treat refractory cases of post-zoster eosinophilic dermatitis, deviating from the more common topical corticosteroid therapy. The differential diagnosis of post-zoster eosinophilic dermatitis includes eosinophilic diseases such as eosinophilic pustular folliculitis, angiolymphoid hyperplasia with eosinophilia, and Kimura's disease, which require careful clinicopathologic investigation. This case adds to a new treatment option to our limited understanding of post-zoster eosinophilic dermatitis and its management.