Psoriasis: differential diagnosis

Differential diagnosis of psoriasis including plaque psoriasis, guttate psoriasis, palmoplantar psoriasis and flexural psoriasis.

Plaque psoriasis



  • Chronic condition affecting about 2% of the population at any age
  • Any area can be affected, but most commonly extensor surfaces
  • Well-demarcated plaques with thick, silvery scale, which bleed if picked


  • Treatment includes emollients, topical vitamin D derivatives or vitamin D/steroid combinations
  • UV light usually beneficial
  • Severe cases require referral to secondary care
  • Phototherapy can be helpful
  • In severe cases, biological agents can be beneficial

Guttate psoriasis
Guttate psoriasis



  • Typically 1-10mm drop-like salmon-coloured papules with surface scale
  • Monomorphic appearance, starts on torso before spreading to limbs
  • Acute onset usually follows URTI from group B haemolytic streptococcus
  • Most common in under-30s age group
  • May be seen in association with beta-blockers and lithium
  • Biopsy can aid diagnosis


  • Usually self-limiting, resolves in weeks to months. Emollients can help
  • May progress to plaque psoriasis
  • In severe cases, phototherapy can be beneficial

Palmoplantar psoriasis
Palmoplantar psoriasis



  • Thought to be a disorder of eccrine sweat glands
  • Affects palms and soles, although 10-20% have psoriasis elsewhere
  • Rarely occurs in children. More common in women than men
  • More common in smokers
  • Differential diagnoses include fungal infections


  • No known cure. If a smoker, advise on cessation
  • Regular application of emollients will help
  • Treatments include topical steroids, acitretin, psoralen plus UVA light
  • In severe cases, biological agents can be beneficial

Flexural psoriasis
Flexural psoriasis



  • Common condition affects armpits, groin, submammary folds, umbilicus
  • Scale usually absent and skin looks red, shiny and smooth
  • Borders usually well demarcated
  • Psoriasis may also be present in non-flexural areas
  • Secondary infections common


  • Treatment includes emollients and topical steroids
  • Vitamin D analogues helpful but may be poorly tolerated due to irritation
  • Topical calcineurin inhibitors are an alternative to steroids
  • Phototherapy is relatively ineffective in most cases

Dr Nigel Stollery is a GP in Leicestershire

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