Dermoscopic Features of Psoriasis

Dermoscopic Features of Psoriasis

Dermoscopy in Psoriasis can be very useful – because it displays repetitive features.

Dermoscopic features of Psoriasis:

  1. Uniformity distributed dotted red vessels which histopathologically corresponds to the dilated capillaries found in the elongated dermal papillae
  2. A light/dull red background
  3. Diffuse white scaling ( histologically corresponding to parakeratosis.

These 3 features combined has good diagnostic accuracy

  • The blood vessels in psoriasis are typically similar in size and shape and are distributed at uniform distance from each other
  • But in the hyperkeratotic lesions – these vessel morphology cannot be appreciated – so on removing the scales we can see tiny bleeding points – this is referred to as “Dermoscopic auspitz sign)

The red dots can also be arranged in – patchy/clustered/ring form

Sometimes the vessels can be seen as red globules (vessels with diameter >0.1mm) and these globules are common in the leg (because of increased hydrostatic pressure)

Dermoscopic differentials:

  1. Dotted vessels and diffuse white scaling – also seen in Bowen’s disease – but vessels here are distributed in focal/clustered pattern and are also different in size, shape and distance among each other
  2. Uniform dotted/globular vessels – seen in LSC and secondary lichenification. But here the vessels are typically surrounded by a white halo due to the presence of hypergranulosis

Based on body sites/types – there is not much difference in the dermoscopic features except in the amount of scaling

  • Guttate psoriasis – little or absent scaling
  • Flexural psoriasis – lack scaling
  • Pustular psoriasis – yellow globules and crusts are seen along with dotted vessels and white scales
  • Follicular psoriasis – white follicular keratotic plugs which is surrounded by dotted vessels which are arranged uniformly

Also dermoscopy reveals skin atrophy that is not evident clinically – following chronic treatment with potent topical steroids which causes appearance of telangiectatic vessels.

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M.D DVL Post Graduate, Madras Medical College and RGGGH Chennai

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