How is psoriasis morphology?

➢ The typical lesion is a well-demarcated, pink to salmon colored plaque covered by loosely adherent silver-white scale Histology ➢ Marked epidermal thickening (acanthosis), with regular downward elongation of the rete ridges. ➢ The pattern of this downward growth has been likened to “test tubes in a rack.” ➢ Increased epidermal cell turnover and lack of maturation results in loss of the stratum granulosum and extensive parakeratotic scale. ➢ Also seen is thinning of the epidermal cell layer overlying the tips of dermal papillae (suprapapillary plates), and dilated and tortuous blood vessels within the papillae. ➢ These vessels bleed readily when the scale is removed, giving rise to multiple punctate bleeding points (Auspitz sign) ➢ Neutrophils form small aggregates within both the spongiotic superficial epidermis and the parakeratotic stratum corneum. ➢ Similar changes can be seen in superficial fungal infections, which need to be excluded with appropriate special stains