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Psoriasis is a chronic skin condition, characterised by cutaneous inflammation and epidermal hyperproliferation. The course of the disease often follows a relapsing and remitting pattern. 




  • Prevalence: 1-2% in the general population
  • Onset: Late teens/early adulthood (Type I psoriasis; may be accompanied by a positive family history)
  • Second peak occurs during 50s/60s (may be referred to as Type II psoriasis)
  • Affects both men and women equally



    The exact cause is unknown, however a number of “triggers” have been implicated



    • Keratinocyte hyperproliferation 
    • T-cell mediated inflammatory infiltration 


      Clinical Features

      Psoriatic lesions may be described as follows:

      • Erythematous 
      • Silver/ scaly (if flexural, there is usually no scaling, but rather a shiny surface)
      • Raised and well-defined 
      • Removal of the plaque surface may lead to pin-point bleeding (Auspitz Sign)
      • The lesions may itch



      The clinical pattern depends on type of psoriasis;

      • Plaque: Affects the extensor regions such as the elbows, knees, scalp, behind the ears and the lumbro-sacral region.
      • Flexural; Affects body folds such as the axilla and the groin
      • Guttate: (“Gutta” = Latin for tear drop) Associated with post-streptococcal throat infection in children. Lesions have the appearance of rain/tear drops, hence the term. This may affect the trunk, limbs and the back
      • Palmar/plantar pustular psoriasis (PPPP): Pustular lesions affecting the hands and feet 



      Associated features

      Nail changes

      • Onycholysis (separation of nail from the nail bed)
      • Pitting
      • Hyperkeratosis.


      Psoriatic arthritis

      • Part of the sero-negative spondyloarthritides
      • Dactylitis/ “sausage digit"
      • This pattern of arthritis may present in a similar pattern to rheumatoid hands. *This is an important differential diagnosis in exams!*
      • Arthritis mutilans (“Telescoping” of the distal phalanges into the proximal phalanges; extremely severe joint deformity)



      Diagnosis is made upon clinical assessment. Skin biopsies and laboratory investigations are rarely required 

      Possible differential diagnosis of scaly rash

      • Lichen planus 
      • Eczema 
      • Dermatitis
      • Pityriasis rosea 




      General measures

      • Emollients
      • Avoiding triggers


      Medication depends on the severity of the condition

      1)Topical treatment (mild psoriasis)

      • Emollients/tar-based cream
      • Salicyclic acid ointments
      • Topical steroids
      • Vitamin D analogues


      2) Phototherapy (moderate to severe psoriasis)

      • Ultraviolet B light
      • Psoralen UVA (PUVA) - Psoralen increases the uptake of UVA into the skin


      3) Oral/ systemic treatment (severe psoriasis)

      • Methotrexate
      • Oral retinoids
      • Ciclosporin
      • Hydroxycarbamide
      • Fumaric acid esterase


      Dermatological Examination


      • Name
      • Age
      • Consent
      • Exposure: Ensure patient is fully exposed; ensure dignity is maintained by providing a gown


      Ask about any pain or tenderness



      When inspecting, comment on:

      • Location of plaques/lesions (scalp, hair, behind the ears, elbows, trunk, buttock-region, knees)
      • Distribution: Extensor surfaces
      • Comment on appearance of lesions, symmetry, definition, colour, size, number of lesions



      • Palpate over the surface of each lesion, and comment on the edges, surface and smoothness
      • Ask the patient if they have other lesions in hidden areas


      Further examination

      • Hands: Nail changes (pitting; onycholysis), arthritic changes
      • Behind the ears




      The classic terms to describe a psoriatic lesion are:

      "This is a erythematous, well-defined, lesion with a silver plaque, distributed symmetrically over the extensor surfaces of the body."


      Further useful reading:



      Images on the various types of psoriasis may be found here:






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