Atrichia and papular lesions: report of a case.

We report a case of atrichia with papular lesions in a 4-year-old girl. The scalp was completely hairless since birth, except for dark, shiny, coarse hair on the frontoparietal region. Eyelashes and eyebrows were sparse. Numerous papular lesions developed on the hairless scalp, cheeks and neck during the second year of life. Teeth and sweating function were normal. The family history was negative. Histologic examination of a papular lesion showed the presence of a keratin-filled cyst in contact with the overlying epidermis. The pathology of the bald scalp showed the presence of tubular epithelial structures devoid of hair bulbs extending from the epidermis to the deep dermis and the superficial hypodermis. Sebaceous and outer root sheath differentiation was evident in most of the tubular structures that also frequently contained small ducts surrounded by two or three layers of flat epithelial cells. The superficial dermis contained horny cysts, similar to those present on the cheeks.