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Section 3 Psoriasis and Psoriasiform Dermatoses 51
Figure 3-2. Psoriasis vulgaris: buttocks (guttate type) Small, discrete, erythematous, scaling,
papules that tend to coalesce, appearing after a group A streptococcal pharyngitis. There was
a family history of psoriasis.
Figure 3-3. Psoriasis vulgaris: elbow Chronic stable
plaque psoriasis on the elbow. In this location, scales
can either accumulate to oyster shell-like hyperkeratosis,
or are shed in large sheets revealing a beefy-red base.
This plaque has arisen from the coalescence of smaller,
papular lesions that can still be seen on lower arm.
lesion is extremely chronic, it adheres tightly
resembling an oyster shell (Fig. 3-3).
Distribution and Predilection Sites
Acute Guttate. Disseminated, generalized, mainly
trunk.
chronic Stable. Single lesion or lesions localized
to one or more predilection sites: elbows, knees,
sacral gluteal region, scalp, and palm/soles
(Fig. 3-5). Sometimes only regional involvement
(scalp), often generalized.
Pattern. Bilateral, often symmetric (predilection
sites, Fig. 3-5); often spares exposed areas.
Psoriasis in Skin of color. In dark brown or black
people psoriasis lacks the bright red color. Lesions
are brown to black but otherwise their morphology
is the same as in white skin (Fig. 3-6).
Special Sites
Palms and Soles. May be the only areas involved.
There is massive silvery white or yellowish hyperkeratosis,
which is not easily removed (Fig.
3-7). The inflammatory plaque at the base is
always sharply demarcated (Fig. 3-7A). There
may be cracking, painful fissures and bleeding.
Scalp. Plaques, sharply marginated, with thick
adherent scales (Fig. 3-8). Often very pruritic.
Note: Psoriasis of the scalp does not lead to hair
loss. Scalp psoriasis may be part of generalized
psoriasis or the only site involved.