SEBORRHEA AND DRY DESQUAMATION

Miliaria

Secretion of sweat normally exudes from the glands but occasionally collects in the gland ducts, distending them so that they are visible at birth as discrete pinpoint elevations known as milia crystalline (Figure 21.1). They usually disappears during the first week of life. They are most often visible on the forehead, cheeks, and sides of the nose. Microscopically a keratinous plug and an intra- or subcorneal vesicle communicates with the underlying sweat duct, sometimes with a mild inflammatory infiltrate. When the process is deeper, prickly heat (miliaria rubra) occurs.

Milia are pearly yellow 1 to 3-mm papules on the face, chin, and forehead of 50% of newborns. Occasionally they erupt on the trunk and extremities. Although milia usually resolve without treatment during the first month of life, they may persist for several months. Microscopically they are miniature epidermal inclusion cysts, which arise from the pilosebaceous apparatus of vellus hairs.

Seborrheic Dermatitis

The scalp is most often affected in the newborn and is often associated with incomplete removal of the vernix caseosa. The lesions are poorly defined, yellowred salmon-colored patches covered by waxy, greasy, easily removed scales.

Acanthosis, edema, and occasional perivascular infiltration of leukocytes are present as well as spongiosis of the basal layer seen microscopically (Figure 21.2).