Pustules may be classified on the basis of where the acute inflammatory cells accumulate (e.g., subcorneal, follicular), pathogenesis (e.g., infectious, autoimmune), predominant inflammatory cells (e.g., neutrophils, eosinophils), and clinical presentation (Table 11-1). Pustules may be unilocular or multilocular.

Acne vulgaris, although not all lesions in this condition are pustular (Fig. 11-1). The infectious pustular eruptions are also common (see Chapter 27).

Pustular psoriasis may be broadly subdivided into localized and generalized forms. Localized pustular psoriasis may occur on any site and may also occur within plaques of classic psoriasis. Distinctive variants include acrodermatitis continua of Hallopeau (Fig. 11-2A), which is characterized by pustules and crusting of the distal fingers and toes, and localized pustular psoriasis of the palms and soles (Fig. 11-2B). It is unclear whether pustular eruptions confined to the palms and soles represent a form of localized psoriasis or a different disease called pustular bacterid. Variants of generalized pustular psoriasis include generalized pustular psoriasis of von Zumbusch, exanthematic generalized pustular psoriasis, and impetigo herpetiformis. The von Zumbusch variant presents as generalized pustules in patients with preexisting plaque-type psoriasis or erythrodermic psoriasis. Exanthematic generalized pustular psoriasis arises suddenly without preceding psoriasis (Fig. 11-2C). Impetigo herpetiformis is associated with pregnancy. Hypocalcemia is also frequently present.