Keratinocyte Differentiation in Psoriatic Scalp: Morphology and Expression of Epithelial Keratins

The study examined hair follicles in psoriatic scalp biopsies compared to normal scalp and found that psoriasis did not affect the lower outer root sheath and hair matrix, although there was an irregular expansion in the proximal lower outer root sheath, identified as the stem cell region. There was also significant shrinkage of sebaceous glands in psoriatic scalp. Keratin expression was generally unaffected by psoriasis, except for the widespread expression of suprabasal keratins K16 and K17 in the psoriatic scalp epidermis. Keratins K8 and K18 were absent in follicular epithelium from both normal and psoriatic scalp. The study concluded that keratin K17 is induced suprabasally during epidermal hyperproliferation and is not hair follicle-specific.