Plaque psoriasis or Psoriasis vulgaris (common type) – affects between 58% and 97% of all psoriasis cases. The difference in prevalence can be explained by race and geographical placement.1
It is characterized by sharply demarcated erythematous (red), silvery (whitish/yellowish), scaling plaques which most commonly occur on the elbows, knees, scalp, chest, back, and groin regions. The lesions are well-defined round or oval plaques that differ in size and in chronic plaque psoriasis often coalesce to form very large lesions covering large areas of the body. Other involved areas include the ears, glans penis, perianal region, and sites of repeated trauma.
The lesions vary in size from 0.5 cm in diameter to large confluent areas on the trunk and limbs. There is a sharp line of demarcation between a plaque and clinically normal, uninvolved skin. Longitudinal studies of individual plaques have demonstrated that plaques are dynamic with an active and expanding edge, sometimes to the extent that the advancing edge may become annular leaving clinically normal skin in the centre of the original plaque.2,3
Plaque psoriasis can present in several different ways.
|Figure 1. Plaque Psoriasis – colour varies from pinkish red to deep red, shiny with minimal silvery scale. Multiple lesions often coalesce forming larger plaques. This patient would be classified has having sever psoriasis|
|Figure 2. Plaque Psoriasis – Rupioid subtype Deep violaceous annular (round) lesions with distinctive, thickened, silvery scale. Multiple small lesions can be seen to be coalescing.|
The term rupioid relates to distinct morphological subtype of plaque psoriasis. Rupioid plaques are small (2–5 cm in diameter) and highly hyperkeratotic, resembling limpet shells (see Figure 2).
A white blanching ring, known as Woronoff’s ring, may be observed in the skin surrounding a psoriatic plaque.
Other morphological subtypes of plaque psoriasis:-
- Psoriasis gyrate — Figure 3 – in which curved linear patterns predominate annular psoriasis (psoriasis annularis – see figure 7 & 8) )—in which ring-like lesions develop secondary to central clearing
- Psoriasis follicularis — Figure 4 – in which minute scaly papules are present at the openings of pilosebaceous (hair) follicles.
- Ostraceous psoriasis (see Figures 5 & 6 below) refers to hyperkeratotic plaques – extremely thick scaled plaques often resembling an oyster shell.
Figure 5 Figure 6
Plaque psoriasis (see Figures 7 & 8 below) with a discoid (circular or oval) appearance is called psoriasis annularis or annular psoriasis.
Figure 7 Figure 8
Scale is typically present in plaque psoriasis, is characteristically silvery white, but may appear a yellowish colour and can vary in thickness.
Removal of scale may reveal tiny bleeding points (Auspitz sign – See Figure 9). The amount of scaling varies among patients and even at different sites on a given patient. In acute inflammatory or exanthematic psoriasis, scaling can be minimal and erythema may be the predominant clinical sign.4
- Lichenified psoriasis (Figure 10 and 11) – thickened psoriasis caused by chronic scratching (eczematized)
Figure 10 Figure 11
Elephantine psoriasis (Figure 12 and 13) – large persistent, leathery plaques
Figure 12 Figure 13
Presentation examples of Plaque Psoriasis
Read also “Psoriasis – Severity and Types”