Reactive perforating collagenosis (RPC) is one of the four essential acquired perforating dermatoses. The condition is characterized by the transepidermal elimination of altered collagen. This paper describes four patients with a giant variant of RPC which has not previously been documented. Three of the patients had associated diabetes mellitus and one had chronic renal failure secondary to fetal scarring. Three of the four patients had a significant improvement in their lesions and symptoms following treatment with allopurinol.