79
Perforating Disorders
Classically, a group of disorders in which there is transepidermal elimination (‘perforation’) of components of the dermis, in particular collagen and/or elastic fibers (Table 79.1). Etiologies are multiple, including inheritance as an isolated cutaneous disease or in association with genetic disorders that affect connective tissue (e.g. Ehlers–Danlos syndrome). Most commonly, however, the perforating disorder is acquired and is related to the cutaneous trauma that results from scratching pruritic skin, especially in the setting of chronic kidney disease. A number of other cutaneous diseases occasionally undergo perforation, e.g. granuloma annulare, calcinosis cutis, chondrodermatitis nodularis helicis.
Table 79.1
Major perforating disorders.
* Occasionally affects patients with pruritus due to other disorders, e.g. Hodgkin disease, biliary cirrhosis.
Courtesy, Ronald Rapini, MD.
Acquired Perforating Dermatosis (APD)
• The most commonly observed perforating disorder (see Table 79.1); it is an acquired disease that affects primarily adults; the term APD encompasses several overlapping entities including acquired reactive perforating collagenosis (RPC), Kyrle’s disease, and perforating folliculitis.
• Erythematous, skin-colored or hyperpigmented papules and papulonodules with a central keratotic core that favor the extensor surfaces of the extremities (Figs. 79.1 and 79.2); the central core is a reflection of the transepidermal elimination of collagen and/or elastic fibers as well as hyperkeratosis associated with epidermal hyperplasia.
Fig. 79.1 Acquired perforating dermatosis. Numerous papules and papulonodules on the legs in a patient with diabetes mellitus and chronic kidney disease. Courtesy, Ronald Rapini, MD.
