Psoriasis

Typical Patient

• usually early adult life

• can be infant to old age

• family history - 16% if one parent, 50% if both

History

• pink/red plaques or annular lesions

• scaling

• well defined

• not usually itchy

• distribution

  • elbows

  • knees

  • scalp

  • sites of injury (Köbner's phenomenon)

• nails

  • pitting

  • onycholysis

DHx

• can be exacerbated by

  • alcohol

  • beta-blockers

  • NSAIDs

  • Lithium

Examination

• Observation

  • generalised skin changes

• Hands

  • nails

    • pitting

    • ridging

    • onycholysis

    • hyperkeratosis

    • discolouration

  • skin

    • plaques

    • sausage-shaped fingers

  • Joints

    • DIP joint swelling

    • rheumatoid pattern of symmetrical small joint swelling

    • arthritis mutilans

    • monoarthritis of large joints

    • ankylosing spondylitis

    • sacroiliitis

  • Rash

    • salmon pink plaques

    • silver-white scales

• Other

  • extensor surfaces

  • scalp

  • navel

  • natal cleft

Variations

• guttate psoriasis

• pustular psoriasis

• flexural psoriasis

• napkin psoriasis

• generalised pustular psoriasis

• erythrodermic psoriasis

  • life-threatening

  • can spread rapidly, especially if irritated by tar, UV light, etc.

Pathology

• increased epidermal turnover

• dilated / tortuous blood vessels - "Auspitz sign"

• polymorphs → sterile pustules

• beta-haemolytic streptococci throat infection can lead to guttate psoriasis

Investigations

Treatments

• emollients

• coal tar preparations

• dithranol

• calcipotriol

• corticosteroids

  • produce severe rebound when stopped

• PUVA / UVB

• methotrexate

• acitretin

• cyclosporin A

Prognosis

• can be cleared after some time

• will probably recur

Complications

• seronegative arthropathy (10%)

  • distal interphalangeal joints

  • single large joint

  • spondylitis

  • arthritis mutilans

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