S2C13P7PsoriasicMisc

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S2C13P7-1a&b (superficial fungus infection): The patterns are somewhat psoriasiform, but the defining feature is the subcorneal pustule. The papillary dermis is edematous, a common feature of the subcorneal pustular disorders. The pustule is richly cellular and the keratin layer is relatively normal. There are lytic defects among keratinocytes in the superficial unit beneath the defect. The pattern in the superficial unit of the epidermis is both spongioform and pustular.

S2C13P7-2 a & b (superficial fungus infection): This lesion is more obviously psoriasiform than the lesion in P7-1, at least in regard to rete patterns. In addition, a subcorneal pustule is not represented. There is, however, an inspissated pustule in a parakeratotic cap in P7-2 a & b to the extreme right of each field.

The patterns in S2C13P7-2 are psoriasiform; those in P7-1 are richly pustular and subcorneal; in both lesions a PAS stain showed branching fungal hyphae in the keratin layer and at the interface between the keratin layer and the viable epidermis. In these two examples, the relationships between an offending agent in the keratin layer and a distinctive reaction pattern in the epidermis are clearly defined, but not exhausted.

S2C13P7-3 (Reiter’s disease): the patterns of the lesion to the left are psoriasiform. An expression of a thick parakeratotic scale with inspissated pustules in layered patterns is extreme. There is evidence of cytolysis in some keratinocytes near the interface between the viable superficial unit and the keratin layer.

With this example, the spectrum of psoriasiform disorders is extended to include an infectious disorder with severe systemic manifestations. The thick scale in itself is a clue to the nature of the process. The patterns are compatible with those seen in cutaneous lesions of Reiter’s disease.

S2C13P7-4 a & b (to the left) (pityriasis rubra pilaris): The epidermis shows compact hyperkeratosis, a prominent granular layer, and acanthosis. Rete patterns are irregular and partially effaced . In P7-4b, there is a localized area of inter- and intra-cellular edema with some loss of nuclear polarity. There are spotty areas of liquefaction degeneration at the dermal-epidermal interface. The upper portion of the dermis shows mild perivascular infiltrates of lymphocytes and histiocytes. A few lymphocytes and histiocytes have collected at the dermal-epidermal interface in the area showing the liquefactive changes.

The changes in P7- 4 by some criteria are compatible with pityriasis rubra pilaris, but clearly some of the descriptions in current textbooks are giving recognition to a different process. The pattern in P7- 4 has some of the qualities of an interface disorder. For this group of images, as seen in P7-4, it is difficult to extend the definition of psoriasiform disorders to include pityriasis rubra pilaris. It is most likely that PRP (pityriasis rubra pilaris) currently is a generic category embracing several different processes.

S2C13P7-5: The four figures above are all purported examples of PRP. If frequency of particular patterns is a guide to the appropriateness of a diagnosis, these psoriasiform patterns might be judged to be more representative of PRP than the poorly developed interface pattern of P7-4. Two of the figures do show mild liquefactive changes at the dermal-epidermal interface.

S2C13P7-6(above) (linear psoriasis): This linearly distributed lesion is an example of linear psoriasis. Isomorphism is represented.



	S2C13P7-7a & b (above and to the right, respectively): The histologic pattern of the lesion in P7-6 is illustrated. The patterns are clearly those of a psoriasiform process. A small spongiotic vesicle is present in the parakeratotic cap. In slide b, the patterns in the epidermis have a spongioform pustular quality (LINEAR PSORIASIS).

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