Erythema toxicum neonatorum: An immunohistochemical analysis

Erythema toxicum neonatorum is a benign rash of unknown etiology, present t o various degrees in most term newborns and characterized by an accumulatio n of eosinophils in dermal lesions. The recruitment of leukocytes to tissue s implicates the involvement of adhesion molecules, cytokines, and chemokin es. We therefore performed immunohistochemistry on punch biopsy specimens f rom cutaneous lesions of ten 1-day-old infants with erythema toxicum using specific monoclonal antibodies directed against a variety of adhesion molec ules, cytokines, chemokines, and cell type-specific membrane markers. Biops y specimens of noninflamed skin from four matched newborns and four adults served as controls. The immunohistologic features of erythema toxicum in al l in infants included a strong staining of the adhesion molecule E-selectin in the Vessel wall and the presence of numerous inflammatory cells that we re identified as dendritic cells (CD1a, CD83, HLA-DR, CD40, and ICAM-1 posi tive), eosinophils (EG2 positive), neutrophils (CD15 positive), macrophages (CD14, CD68, and Mac387 positive), and E-selectin-expressing cells. Furthe rmore, the lesions showed a high incidence of the proinflammatory cytokines interleukin (IL)-1 alpha and IL-1 beta and of the chemokines IL-8 and eota xin. This immunologic activity was reduced or absent in noninflamed skin fr om newborn controls and adults. We conclude that there is an accumulation a nd activation of immune cells in the lesions of erythema toxicum, also pres ent in noninflamed skin of 1-day-old infants, but to a lower level. The phy siologic significance of the rash remains to be elucidated.