Benign skin lesions in the newborn are reviewed here. Blistering conditions in the newborn caused by infection, congenital abnormalities, infiltrative disease, vascular lesions, and congenital nevi are discussed separately. (See "Vesiculobullous and pustular lesions in the newborn" and "Skin nodules in newborns and infants" and "Vascular lesions in the newborn" and "Congenital melanocytic nevi".)
Benign vesiculopustular lesions — Although most vesiculopustular eruptions in newborns are benign and self-limiting, the differential diagnosis includes conditions that require prompt recognition and/or therapy (table 1). (See "Vesiculobullous and pustular lesions in the newborn".)
Erythema toxicum neonatorum — Erythema toxicum neonatorum (ETN) occurs in 31 to 72 percent of full-term infants but declines in incidence with decreasing birth weight and gestational age . The etiology is not known, but immaturity of the pilosebaceous follicles (the combined sebaceous gland and hair follicle) may contribute .
ETN is characterized by multiple erythematous macules and papules (1 to 3 mm in diameter) that rapidly progress to pustules on an erythematous base (picture 1A-B) . The lesions are distributed over the trunk and proximal extremities, sparing the palms and soles. They may be present at birth, but typically appear within 24 to 48 hours. The rash usually resolves in five to seven days, although it may wax and wane before complete resolution .
The diagnosis of ETN is usually made upon the basis of clinical appearance. It can be confirmed by microscopic examination of a Wright-stained smear of the contents of a pustule that demonstrates numerous eosinophils and occasional neutrophils. However, this usually is not necessary. A minority of patients (7 to 18 percent) may also have peripheral eosinophilia .