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Case of acquired reactive perforating collagenosis induced by panitumumab for colon cancer

Dear Editor, Panitumumab, the first fully human anti-epidermal growth factor receptor (EGFR) monoclonal antibody, is used for treating colon cancer. Cutaneous toxicity is frequently seen such as paronychia and acneiform rash. Here, we report a case of acquired reactive perforating collagenosis (ARPC) induced by panitumumab. A 62-year-old woman had been treated with folinic acid, fluorouracil and irinotecan (FOLFIRI) and bevacizumab for advanced colon cancer. She had no medical history of renal failure or diabetes mellitus. After 1 year and 6 months of therapy, computed tomography revealed disease progression; accordingly, the chemotherapy was changed to panitumumab and irinotecan. After six cycles of therapy, she presented with pruritic papular lesions on the back and extremities that did not improve with topical steroid treatment. Physical examination revealed round to oval erythematous papules with collapsed centers and keratotic plugs (Fig. 1a,b). Histopathological examination revealed a cup-shaped invagination that was plugged by basophilic collagen and necrotic inflammatory cells (Fig. 1c). Masson’s trichrome staining showed degenerative collagen fibers seeming to pass through