Psoriasis is a chronic inflammatory skin condition characterised by clearly defined, red and scaly plaques.

 

Psoriasis is an auto-immune mediated genetic disease of the skin. It requires a medical diagnosis and it is categorised into several categories:

• Guttate Psoriasis

  • Post-streptococcal acute guttate psoriasis

  • Widespread small plaques

  • Often resolves after several months

• Small plaque psoriasis

  • ​Often late age of late-onset

  • ​Plaques <3 cm

• Chronic plaque psoriasis

  • Persistent and treatment-resistant

  • Plaques >3 cm

  • Most often affects elbows, knees, and lower back

  • Ranges from mild to very extensive

• Unstable plaque psoriasis

  • The rapid extension of existing or new plaques

  • Koebner phenomenon: new plaques at sites of skin injury

  • Induced by infection, stress, drugs, or drug withdrawal

• Flexural psoriasis (inverse psoriasis)

  • Affects body folds and genitals

  • Smooth, well-defined patches

  • Colonised by candida yeasts

• Scalp psoriasis

  • Often the first or only site of psoriasis

• Sebopsoriasis

  • Overlap of seborrhoeic dermatitis and psoriasis

  • Affects the scalp, face, ears and chest

  • Colonised by malassezia

• Palmoplantar psoriasis

  • Affecting the palms and/or soles

  • Keratoderma

  • Painful fissuring

• Nail psoriasis

  • Pitting, onycholysis, yellowing, and ridging

  • Associated with inflammatory arthritis

• Erythrodermic psoriasis

  • Erythrodermic psoriasis is rare.

  • May or may not be preceded by another form of psoriasis

  • Acute and chronic forms

  • May result in systemic illness with temperature dysregulation, electrolyte imbalance, or cardiac failure

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What are the clinical features of psoriasis?

Psoriasis usually presents with symmetrically distributed, red, scaly plaques with well-defined edges. The scale is typically silvery white, except in skin folds where the plaques often appear shiny with a moist peeling surface. The most common sites are the scalp, elbows, and knees, but any part of the skin can be involved. The plaques are usually very persistent without treatment.

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Itch is mostly mild but may be severe in some patients, leading to scratching and lichenification characterised by thickened leathery skin and increased skin markings. Painful skin cracks or fissures may occur, particularly on the palms and soles.

Psoriasis can demonstrate the Koebner phenomenon. This involves the generation of new lesions on the skin that have been damaged or irritated such as by injury, burns etc.

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When psoriatic plaques clear up, they may leave brown or pale marks (postinflammatory hypo- or hyperpigmentation) that can be expected to fade over several months.

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Auspitz sign refers to pinpoint bleeding upon removal of the scaly layer in plaque psoriasis. It is related to the dilated dermal capillaries involved in the histological pathogenesis of chronic psoriasis.

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