Herpes associated erythema multiforme annularis concentricum

A young man had large, concentric plaques over the back and extensors of forearms for eight weeks. Past history suggested recurrent herpes labialis. Serum anti HSV-1 IgG titre was raised to 32 micrograms/l and histopathology of an active lesion suggested erythema multiforme. Symptomatic treatment and oral zinc therapy subsided EM lesions but concentric depigmentation developed after healing