Case 1 A 67-year-old South Korean woman presented with a painful eruption on the left trunk. Several groups of vesicles with an erythematous and edematous base were situated unilaterally within the distribution of the left T9 dermatome; they had been present for 7 days. A diagnosis of herpes zoster was made, and treatment with acyclovir, analgesics, tranquilizers, and wet dressings produced a moderate response. Two weeks after onset, the lesions appeared to have healed with a scar. Four months later, however, the patient noticed another eruption of papules in the postherpetic area (Fig. 1A,B). Figure 1. Case 1. (A) Multiple erythematous papules on the left trunk along the T9 dermatome. (B) Multiple erythematous papules with a keratotic central plug Download figure to PowerPoint The biopsy specimen showed a cup-shaped epidermal invagination filled with a keratotic plug containing basophilic debris and collagen, with perforation of the epidermis. Masson's trichrome stain identified refractile fibers within the epidermis as hyalinized and degenerating collagen. Van Gieson staining for elastic fibers was negative in the epidermis and in the crater. These findings are consistent with reactive perforating collagenosis (RPC). Case 2 A 66-year-old South Korean woman developed herpes zoster of the left neck and shoulder, which resolved after an uncomplicated course. Two months later, a zosteriform, pink, papular eruption developed at the site of the resolved herpes zoster. Examination revealed multiple, erythematous papules with a central umbilication containing a firmly adherent keratotic plug on the left shoulder and neck (Fig. 2A). Figure 2. Case 2. (A) Multiple erythematous papules on the left neck and shoulder along the C4 dermatome. (B) Cup-shaped epidermal invagination filled with keratotic plug containing basophilic debris and degenerated collagen, with perforation of the epidermis (hematoxylin and eosin stain, × 100) Download figure to PowerPoint The biopsy specimen showed a dome-shaped lesion with a central crater that extended from the epidermis to the papillary dermis and contained degenerated collagen in vertical strands (Fig. 2B).