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S2C14P8-1 & 2 (left and right, respectively) (erythroderma): In P8-1, the rete patterns are not greatly accentuated, but there are psoriasiform features. Zones of parakeratosis and the edematous dermal papillae that contain dilated, congested vessels are psoriasiform features. In P -2, the psoriasiform patterns are better developed.

S2C14P8-3a & b (left and right, respectively) (erythroderma): In P8-3a, the hyperplasia of the basal unit of the epidermis has a psoriasiform quality. In addition, there is focal parakeratosis with inflammatory cells in the superficial unit of the epidermis. The papillary dermis is edematous. In P8-3b, one of the basic patterns of a psoriasiform reaction is represented; a pustule involves the superficial unit of the epidermis. In part, the pustule has the qualities of a Munro microabscess and, in part, it has spongioform pustular qualities.

The lesions in S2C14P8-1, 2, & 3 are representative of common patterns encountered in the setting of the erythrodermas. The patterns basically are psoriasiform, but without significant accentuation of the rete patterns. There is basal unit hyperplasia with variable components of parakeratosis. The clinical impression for the lesion represented in P8-2 was psoriasis in an erythrodermic phase. It is extremely difficult to predict the nature of the underlying disorder from the examination of a skin biopsy of an erythroderma. Often the nature of the underlying disease is either established prior to the onset of the erythroderma, or becomes obvious as the erythroderma subsides and, in the process, comes to present a more characteristic clinical and histologic picture.

S2C14P8-4 & 5 (guttate psoriasis): The changes in both figures are basically the same. The patterns are psoriasiform, but are not those of the standard patterns of classic psoriasis. The rete patterns are somewhat irregular. Parakeratosis is spotty and, at the lower magnification, as seen in P8-4 on the left, the distribution of the parakeratotic caps varies both vertically and horizonally. In P8-5, the dermal papillae are more elongated and club-shaped than in P8-4.

In S2C14P8-4 & 5, the patterns are psoriasiform but are not diagnostic of classic psoriasis. Both lesions are representative of changes seen in the clinical setting of guttate psoriasis. The pattern in P8-4 is as diagnostic of this variant of psoriasis as is the pattern in S2C9P3-2a for classic psoriasis. The alternating zones of parakeratosis lends some specificity to the histologic changes (this is also a feature currently emphasized in the diagnosis of some examples of PRP. Some examples of PRP may be variants of guttate psoriasis.

S2C14P8-6: In this lesion of psoriasis, the basal unit is hyperplastic in a characteristic pattern. Dermal papillae are elongated and club-shaped. In the dermal papillae, vessels are tortuous; they appear to be increased in number. The vascular patterns in the dermal papillae overlap with those of a mild angiodermatitis. Inflammatory disorders affecting the lower extremities are often complicated by varying degrees of angiodermatitis; lesions of psoriasis on the lower extremities often show complicated histologic patterns.

S2C14P8-7: The patterns are psoriasiform and spongiotic; they are both epidermal and follicular (inverse psoriasis).

S2C14P8-8: This is another example of guttate psoriasis. There is basal unit hyperplasia with elongation of rete ridges. Centrally, there is a small area of spongiosis. Parakeratotic caps with Munro microabscesses are scattered along the surface.

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