Corneocytes in scaly parakeratotic diseases

The stratum corneum of some of the scaly (parakeratotic) diseases was examined with light and scanning electron microscopy (SEM) with the purpose to reveal the importance of this layer in the diagnosis of some of the diseases associated with the formation of scales.

Two biopsies of the skin surface were taken: one, obtained from 80 patients with various parakeratotic scaly diseases and from 25 control subjects, was processed for light microscopy; the other biopsy for SEM was taken from 10 control subjects and 25 patients. The diagnoses of these patients were: psoriasis (5 patients), erythrodermic psoriasis (2 subjects), parapsoriasis (5 patients), pityriasis rubra pilaris (5 subjects), pityriasis rosea (3 subjects), and seborrheic dermatitis (5 subjects).

The light microscopic studies showed that normal corneocytes are of polygonal shape with their largest diameter measuring 42 microns; these cells lacked nuclei. All parakeratotic cells appeared bizarre in shape, smaller than normal, and the cells contained a nucleus. With SEM, normal cells appeared relatively regular in size and shape, trabeculated, and had a flat surface. Cells examined in all the diseases revealed various sizes, outlines, and trabeculae. Specific surface patterns (print) of diseased cells were: "fish-scale" in psoriasis; "marbled" in parapsoriasis, "rocky stone" in pityriasis rubra pilaris; "heart-shaped" in seborrheic dermatitis, and semicrystalloid in pityriasis rosea.

Parakeratosis is characterized not only by the retention of the nucleus in keratinocytes, but is also characterized by a cell of smaller size. The specific print of a disease helps in the diagnosis. The print will change with different stages of a disease.