Published on 08/03/2015 by admin
Filed under Dermatology
Last modified 08/03/2015
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Chapter 8
Dirk M. Elston
Key features
• Neutrophils above parakeratosis in stratum corneum
• Little to no serum in stratum corneum
• Alternating neutrophils and parakeratosis in the stratum corneum (sandwich sign)
• Neutrophilic spongiform pustules
• Little spongiosis in adjacent epidermis
• Tortuous blood vessels in dermal papillae
The appearance of psoriasis depends on the stage of the lesion and type of lesion. Early guttate lesions demonstrate no acanthosis. Established plaques demonstrate a characteristic pattern of regular acanthosis. Pustular psoriasis may never demonstrate acanthosis. Acral and intertriginous lesions of psoriasis commonly demonstrate a background of spongiosis, but spongiosis is distinctly absent from the surrounding epidermis in most other locations. Reiter’s disease and geographic tongue histologically look like psoriasis.
Pearl
Collections of neutrophils within the stratum corneum:
• Psoriasis, tinea, impetigo, Candida, seborrheic dermatitis, syphilis (PTICSS)
• Regular bulbous club-shaped acanthosis
• Thin superpapillary plates
Fig 8-1 Plaque psoriasis
• Collections of neutrophils within stratum corneum
• Subcorneal pustules
• Spongiform pustules
Fig 8-2 Pustular psoriasis
Subcorneal pustules: Candida, acropustulosis of infancy, transient neonatal pustular melanosis, Sneddon–Wilkinson (and IgA pemphigus), impetigo, pustular psoriasis, Staphylococcus scalded-skin syndrome (CAT SIPS, or an anagram of SIPS)
• Neutrophils above parakeratosis
The key histologic feature of guttate psoriasis is a focus of neutrophils on top of parakeratosis (half of the sandwich sign, jelly up). The neutrophilic focus may be small and only visible in step sections. The focus often has a hump-like configuration or resembles a child’s drawing of a seagull.
Fig 8-3 Guttate psoriasis
• Alternating ortho- and parakeratosis from left to right
• Areas of orthokeratosis have a prominent granular layer
• Areas of parakeratosis lack an underlying granular layer (see Chapter 2)
Fig 8-4 Inflammatory linear verrucous epidermal nevus (ILVEN)
• Epidermal collections of lymphocytes
• Lymphocytes hyperchromatic and surrounded by white space (lump of coal on a pillow)
• Epidermal lymphocytes larger, darker, and more angulated than lymphocytes in dermis
• Papillary dermal fibrosis
• In areas, lymphocytes may also line up along the dermal epidermal junction
• Bare underbelly sign (see Chapters 7 and 24)
Fig 8-5 Psoriasiform mycosis fungoides
• Vacuolar interface dermatitis together with elongated psoriasiform acanthosis
• Vacuolar interface dermatitis together with interstitial dermal infiltrate (busy dermis)
Dermatopathology
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