Histopathologic study of scalp psoriasis: peculiar features including sebaceous gland atrophy

In a study on scalp psoriasis of 19 patients (11 males and 8 females, 15-64 years of age, psoriasis area severity index partial score of the head ranging from 0.5 to 2.8), we came to notice that, apart from the classical criteria for the diagnosis of psoriasis which were present in all cases, in a majority of patients, sebaceous glands were extremely reduced in size. We compared findings of follicular counts and sebaceous glands with a nonpsoriatic group of individuals (n = 26). Ten cases from the psoriatic population presented with completely atrophic glands, most of the time intermingled with larger glands (P = 0.03); not a single case showed sebaceous gland atrophy in the control group. There were no statistical differences regarding total number of hair follicles (P = 0.08), terminal follicles (P = 0.15), vellus follicles (P = 0.39), and telogen follicles (P = 0.58) between the groups. Other unusual features observed in the scalp psoriasis group were dilation of infundibula in 11 cases, a papillomatous epidermal surface in 8 specimens, parakeratosis at the lips of infundibular ostia in 8 specimens, mitotic figures in 7 cases, and necrotic keratinocytes in 14 cases. We conclude that psoriasis of the scalp may present itself with unexpected microscopic findings, among them being atrophy of sebaceous glands. Further studies are necessary to clarify why this atrophy develops and if it is specific to psoriasis.