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InflammatoryCommonICD-10 L40.0

Plaque psoriasis

Psoriasis vulgaris; chronic plaque psoriasis

Plaque psoriasis is the commonest variant of psoriasis (~ 80% of cases), an immune-mediated dermatosis affecting approximately 2% of the UK population. It presents with well-demarcated erythematous plaques surmounted by silvery scale, characteristically on extensor surfaces (elbows, knees), scalp, lower back and umbilicus. Skin-oncology relevance includes — frequent clinical mimic of Bowen disease, mycosis fungoides and DLE; increased skin-cancer risk in patients treated with PUVA or long-term ciclosporin / TNF-α inhibitors; de novo psoriasis or flare on immune checkpoint inhibitors (psoriasiform irAE); and nail psoriasis as a frequent DDx of subungual cancer.

CurrentLast reviewed 15 May 2026
Clinical image of Plaque psoriasis
Plaque psoriasis. Image sourced from DermNet New Zealand. Used under CC BY-NC-ND 4.0. No endorsement implied.

Clinical features

  • Well-demarcated erythematous plaques with silvery (micaceous) scale.
  • Auspitz sign — pinpoint bleeding on removal of scale.
  • Koebner phenomenon — new plaques at sites of trauma.
  • Common sites — extensor elbows / knees, scalp (often hairline involvement), lower back, umbilicus, gluteal cleft, ear canal.
  • Nail involvement in ~ 50% — pitting, oil-drop sign, subungual hyperkeratosis, onycholysis.
  • Variants — guttate (post-strep), inverse (flexural), erythrodermic, pustular (von Zumbusch).
  • Associated psoriatic arthritis in ~ 30%; metabolic syndrome, IBD, depression.

Skin-oncology context

  • Mimic of skin cancer:
    • Bowen disease — solitary, well-demarcated; biopsy if asymmetric / non-responsive.
    • Mycosis fungoides — patches / plaques refractory to topical Rx; biopsy if doubt.
    • DLE — photodistribution; follicular plugging.
    • Tinea — KOH-positive.
  • Treatment-related skin-cancer risk:
    • PUVA — cumulative-dose-dependent cSCC and melanoma risk; lifetime limits (~ 200–250 sessions).
    • Ciclosporin long-term — increased cSCC.
    • TNF-α inhibitors — modest increase in skin-cancer risk; surveillance.
  • Psoriasis on ICI therapy — flare or de novo; manage as cutaneous irAE; avoid systemic immunosuppression that compromises anti-tumour activity where possible.
  • Nail psoriasis — frequent DDx of subungual SCC, melanoma, onychomatricoma; consider biopsy when unilateral or atypical.

Management overview

  • Topical — potent corticosteroid + vitamin D analogue (calcipotriol); topical tacrolimus / pimecrolimus for face / flexures; coal tar; dithranol.
  • Phototherapy — narrowband UVB 311 nm first-line; PUVA second-line (cumulative cancer risk).
  • Systemic conventional — methotrexate, ciclosporin, acitretin.
  • Biologics — anti-TNF (adalimumab, etanercept, infliximab), anti-IL-12/23 (ustekinumab), anti-IL-17 (secukinumab, ixekizumab, brodalumab), anti-IL-23 (guselkumab, risankizumab, tildrakizumab).
  • Oral small molecules — apremilast, deucravacitinib.
  • Multidisciplinary — dermatology, rheumatology (psoriatic arthritis), cardiology, mental health.
  • Skin-cancer surveillance — annual whole-body examination in those on long-term systemic / phototherapy.

References

  1. BAD biologic interventions for severe psoriasis guideline 2020.
  2. NICE CG153. Psoriasis: assessment and management. London: NICE; 2012 (last updated 1 September 2017; reviewed 4 March 2025).
  3. Stern RS. The risk of squamous cell and basal cell cancer associated with psoralen and ultraviolet A therapy — a 30-year prospective study. J Am Acad Dermatol; 2012.

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