Reactive perforating collagenosis (RPC) is characterized by umbilicated papules with a central adherent keratotic plug. Histologically, this condition shows transepidermal elimination of altered dermal collagen bundles into a cup-shaped epidermal depression. The present paper describes eight patients with associated diabetes mellitus who meet the diagnostic criteria for the acquired form of RPC (ARPC). Although half of these patients underwent dialysis, the lesions did not tend to develop after dialysis. Pruritus and the Koebner phenomenon were common, and histologically a microvasculopathy was noted in the dermis of all patients. We speculate that this disease is triggered by a cutaneous response to superficial trauma. Furthermore, this response acts synergistically with vasculopathy in the dermis, primarily in the case of diabetes mellitus. A secondary sign of ARPC may be degenerated collagen fibres as a result of transepidermal elimination.