PSORIASIS

A chronic recurrent skin disease characterised by scaling, reddened papules or plaques on the scalp, back of the elbows and front of the knees. Psoriasis can have extra cutaneous manifestation (e.g. arthritis)

The lesions tend to appear at sites of trauma (Koebner’s reaction).

Cause

  • Unknown, but usually genetically transmitted
  • About 30% of cases have a family history

Clinical features

  • Usually in patients 25-40 years old
  • Gradual onset of distinct, red scaling papules which coalesce to form plaques
  • Adherent, silvery white scales, which reveal bleeding points when removed (Ausiptz sign)
  • Worsening psoriasis may lead to total erythroderma
  • Extra articular feature, e.g., pitting or thickening of nail plate with accumulation of debris under the nail plate

Differential diagnosis

  • Fungal infection, lichen planus
  • Mycosis fungoides
  • Seborrhoeic dermatitis
  • Medicine-induced eruptions

Investigations

  • Diagnosis is largely clinical
  • Blood: Serum uric acid, rheumatoid factor, and antinuclear factor and histology to rule out other diseases like
    rheumatoid arthritis, SLE, skin malignancies etc.

MANAGEMENT

  • Remove scales, then apply medicine as below

Mild cases (lesions <20% of the body)

  • Give topical steroids, e.g. betamethasone cream applied on the lesions once in the morning
  • Apply crude coal tar ointment 1% at night for 2 weeks

Severe cases (lesions >20% of the body surface area)

  • Refer for specialist management

Caution

  • Drugs that precipitate/exacerbate psoriasis include lithium, beta-blokers, antimalarials and systemic
    steroids