The relationship between bacteria and the abnormal follicular keratinization in acne vulgaris.

The structural organization and bacteriological profile of follicular casts and early comedones in prepuberal children were investigated. Follicular casts were present in all samples but were not as abundant as usually seen in older individuals with acne. When examined with the light microscope, all casts and comedones were composed of numerous layers of horny cells and sebum, but were devoid of bacteria. Neither follicular casts nor comedones yielded bacteria when cultured. Electron microscopy of the follicular casts revealed the presence of small round, discrete lipid droplets, and alternating dense and less dense lamellar configurations within the horny cells. Some horny cells closest to the sebum-filled lumen contained large lipid masses, resulting in "balloon-shaped" regions. Prepuberal follicular horny cells contained all of the abnormalities usually seen in follicular casts and biopsy material from acne patients, which suggests that these casts are potential comedones. These aberrations occurred in the complete absence of bacteria indicating that bacteria are not essential to the formation of casts or comedones. Furthermore, our findings indicate that bacteria play little if any role in the initial events of pathological keratinization.