Psoriatic plaque. Credit: Haley Otman, CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons
Nail pitting. Seenms, CC BY-SA 3.0, via Wikimedia Commons
Onycholysis. Credit: CopperKettle, CC BY-SA 3.0, via Wikimedia Commons

Clinical features

  • Distribution
    • Plaque psoriasis (>90%)
      • Sharply-demarcated plaques covered by silvery lamellar scales
      • Typically on extensor surfaces of forearms and legs, peri-anal region, retro-auricular space and scalp
    • Guttate psoriasis
      • Small erythematous papules
      • Often in children
      • Usually preceded by streptococcal URTI
      • One-third develop plaque psoriasis later in life
      • Often affects face and genito-anal region
    • Eruptive psoriasis
      • Numerous scaly, tear-drop spots
    • Intertriginous (inverse) psoriasis
      • Occurs on flexure surfaces
      • Also on intertriginous areas
      • Usually non-scaly because of friction at these sites
    • Pustular psoriasis (palmoplantar pustulosis or generalized pustular psoriasis)
      • Usually in patients with plaque psoriasis, but may be first presentation
      • Characterized by blister formation
      • Generalized pustular psoriasis characterized by erythema with overlying pustules
  • Nail changes
    • Pitting
    • Yellow or brown patches underneath the nail plate
    • Onycholysis
  • Trigger factors
    • Mild trauma (Koebner phenomenon)
    • Drugs
      • β blockers
      • Prednisolone withdrawal
      • Non-steroidal anti-inflammatory agents
      • Lithium
      • Antimalarials
    • Occupational exposure to chemicals affecting skin barrier
    • HIV infection
  • Psoriatic arthritis
    • Affects 20-30% of people with psoriasis
    • Patterns
      • Distal (OA type)
      • Symmetrical polyarthritis (RA type)
      • Arthritis mutilans
      • Large joint oligoarthritis
      • Axial disease – spondyloarthritis
    • Extra-articular manifestations
      • Enthesitis (tendon inflammation)
      • Dactylitis
      • Anterior uveitis
    • Presents with inflammatory joint pain
  • Family history
  • Assess function in all patients with arthropathy (GALS screen)

Differential diagnosis

  • Tinea capitis
  • Tinea corporis
  • Seborrheic dermatitis
  • Eczema
  • Lichen planus
  • Pityriasis rosea
  • Pityriasis rubra pilaris
  • Cutaneous lymphoma (Sezary syndrome)

Investigations

  • Full blood count (anaemia of chronic disease)
  • Renal function and liver function tests (prior to starting DMARDs)
  • Erythrocyte sedimentation rate
  • Autoantibodies to rule out RA / SLE: RF, anti-CCP, ANA
  • Consider radiographs of affected joints
  • Ultrasound of painful areas for enthesitis
  • Skin biopsy: epidermal acanthosis, hyperkeratosis and parakeratosis in the cornified layer

Management

  • Multidisciplinary team approach
  • Patient education: chronic condition
  • Skin disease
    • Emollients
    • Topical steroids
    • Topical vitamin D derivatives
    • Topical tacrolimus for intertriginous areas or face
    • Phototherapy (narrow-band UVB, photo-chemotherapy with psoralen plus UVA, PUVA)
      • PUVA has carcinogenic potential
  • Psoriatic arthropathy and severe skin disease
    • Methotrexate
    • Sulphasalazine
    • Leflunomide
    • Ciclosporin
    • Biologics
      • Anti TNF-α: infliximab, etanercept, adalimumab
      • IL-12/IL-23 inhibitor: ustekinumab
      • IL-17 inhibitors: secukinumab, ixekizumab, brodalumab
  • Control of cardiovascular risk factors
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