(GP)

Overview

• Chronic inflammatory skin disease characterised by erythematous, circumscribed scaly papules, and plaques caused by hyperproliferation of keratinocytes
• Age of onset 20-40 years old
• Aetiology → genetic predisposition, immunology, infection, mechanical irritation
• Pathophysiology → abnormal T cell activity stimulates keratinocyte proliferation
• Relapsing clinical course, with symptom-free intervals

Classification:

• Plaque Psoriasis (most common form) → raised inflamed plaque lesions with a superficial silvery-white scaly eruption
  • May be exacerbated by beta blockers, ACEi’s, NSAIDs, Lithium
  • Relieved by exposure to sun
• Flexural Psoriasis → skin is smooth. Occurs on skin creases or flexures (ie. groin, armpits).
• Guttate Psoriasis → widespread, erythematous, fine, scaly papules (water drop appearance) on trunk, arms, and legs. The lesions often erupt after an upper respiratory infection (frequently triggered by a streptococcal infection - fever and sore throat). Tx with phototherapy.
• Psoriatic Arthritis → involvement that causes inflammatory damage and deformity. Often preceeds development of skin lesions.
  • HLA-B27 linked condition
  • Asymmetrical Polyarthritis → typically affecting hands and feet
  • Involves DIP swelling and dactylitis (sausage fingers)
  • Pencil-in-cup deformity of DIP joints on x-ray
  • Tx with NSAIDs and DMARDs (methotrexate)
    • Avoid oral steroids as can cause flare up of skin lesions

Making Diagnosis

Clinical Features:

• Skin Lesions → erythematous, well demarcated scaly papules and plaques on the scalp and extensor surfaces of the knees and elbows
  • Purple/Silvery Plaques
• Joint Swelling or Pain → psoriatic arthritis occurs in 20% of patients with psoriasis