Skin Pathology, Case 4 A 25-year-old male presents to his dermatologist with well-demarcated, scaly, pink to salmon-colored plaques over the elbows. Areas of “pin-point” bleeding are noted when the scales are lifted off the surface of the plaque.

Epidermal thickening (acanthosis) Parakeratosis Downward projections of epidermis = “rete ridges”

Parakeratosis Dermal papillae Dermal papilla with dilated blood vessels (when scale is lifted from plaques minute bleeding is seen – Auspitz sign. This is because of the close proximity of the dilated blood vessels to the overlying parakeratotic scale)

Small cluster of neutrophils in parakeratotic stratum corneum

Psoriasis of the legs

Psoriasis. A rather small amount of the characteristic silvery scale is present on these psoriatic plaques.

Patient with severe psoriatic arthritis. There is marked deformity and destruction of the digits. The nail plates are thickened and hyperkeratotic. Some psoriatic skin lesions are present.