What is plaque psoriasis?
Plaque psoriasis is the most common presentation of psoriasis. It presents as small to large, well demarcated, red, scaly and thickened areas of skin. It most likely to affect elbows, knees, and lower back but may arise on any part of the body.
It tends to be a relatively persistent or chronic pattern of psoriasis that can be improved with treatment but is difficult to clear completely with topical treatments alone. It is characterised by large flat areas (plaques) of psoriasis with typical silvery scale. These plaques may join together to involve very extensive areas of the skin particularly on the trunk and limbs. It is often accompanied by scalp and nail psoriasis.
Types of chronic plaque psoriasis
Most cases of plaque psoriasis are described as 'large plaque' or 'small plaque' psoriasis. The plaques may be localised (e.g. to elbows and knees) or generalised (involving scalp, trunk and limbs).
Large plaque psoriasis
Large plaque psoriasis describes thick, well-demarcated, red plaques with silvery scale. This type of psoriasis often has early onset (<40 years) and may be associated with metabolic syndrome. There's often a family history of psoriasis. It can be quite resistant to treatment.
Small plaque psoriasis
Small plaque psoriasis often presents with numerous lesions a few millimetres to a few centimetres in diameter. The plaques are thinner, pinkish in colour and have a fine scale. They may be well-defined or merge with surrounding skin. Family history is less common. Although it may arise at any age, small plaque psoriasis often arises in those over than 40 years of age. This type of psoriasis often responds well to phototherapy.
Other types of plaque psoriasis
Uncommon subtypes or descriptions of chronic plaque psoriasis include:
- Rupioid psoriasis: limpet-like cone-shaped hyperkeratotic lesions of psoriasis
- Lichenified psoriasis: chronically rubbed or scratched areas of psoriasis that have become very thickened
- Elephantine psoriasis: very persistent, very thickly scaled, large areas of psoriasis
- Ostraceous psoriasis: very thickly scaled, ring-like areas of psoriasis, resembling an oyster shell
- Linear psoriasis: psoriasis arranged in lines along the body (often corresponding to fetal developmental lines)
- Koebnerised psoriasis: psoriasis developing within an area of skin trauma such as injury, infection, surgical wound or scratch mark.
- Photosensitive psoriasis: psoriasis worst in the sun-exposed areas of the face, neck, hands and forearms. Most patients with psoriasis find ultraviolet light very helpful for their psoriasis. A small group experience exacerbations of their rash following sun exposure. In these people, sometimes clear 'sunburn' lines are seen. They may also have typical plaque psoriasis elsewhere. Strict sun protection, usually in combination with other treatment, is required to control this type of psoriasis.
Uncommon forms of plaque psoriasis
Assessment of plaque psoriasis
Patients with chronic plaque psoriasis should be assessed by a dermatologist. Factors considered may include the following:
- Age of onset of psoriasis
- Current age and gender
- Sites affected by psoriasis
- Symptoms (itch, soreness)
- Categorisation of psoriasis (localised or generalised, large plaque or small plaque)
- Extent and severity of psoriasis (often by PASI scoring)
- Functional impairment or disability due to the skin disease (often using DLQI or Dermatology Life Quality Index scoring)
- Health problems including blood pressure, weight and body mass index (BMI)
- Smoking status and alcohol intake
- Current medications for psoriasis and other conditions
- Previous treatments and their effect
- Skin phototype
- Suitability of systemic therapy.
Patients to be treated with systemic therapy will be asked to undertake screening tests to ensure the medication is safe for them and as a baseline.
Treatment of chronic plaque psoriasis
Localised or mild chronic plaque psoriasis is usually managed initially with one or more topical agents. The following agents are usually effective for plaque psoriasis:
If plaque psoriasis is too extensive or severe to be effectively managed with topical treatments alone, phototherapy or systemic agents can be used and are usually very effective at improving and even clearing the psoriasis; these include:
- Biologics including adalimumab, etanercept, infliximab and ustekinumab.
For more information on these and other treatments, see DermNet's page on treatment for psoriasis.