Giant cell lichenoid dermatitis within herpes zoster scars in a bone marrow recipient.

Cutaneous lesions arising in herpes zoster (HZ) scars are rare. We report a 34-year-old woman with acute lymphoblastic leukemia underwent allogenic bone marrow transplant (BMT). Ten days after the BMT, she developed clusters of vesicles over the right neck, scapula, shoulder and chest. She was treated with intravenous acyclovir and foscarnet. One month after the vesiculous episode of HZ she showed 5 mm to 2 cm clustered flat violaceous lichenoid papules and confluent plaques within the HZ scars. Histopathologic examination revealed a inflammatory infiltrate present in the papillary dermis with granulomatous aggregated formed by histiocytes, multinucleated giant cells and lymphocytes. She was treated with topic steroids with significant improvement. Pathologic findings are similar to those of an unusual lichenoid reaction named "giant cell lichenoid dermatitis". We present the first reported case of giant cell lichenoid dermatitis at the sites of HZ scars.