Psoriasis

Psoriasis is a common chronic skin disease characterised by cutaneous inflammation and epidermal hyperproliferation - lesions appear on any part of the skin, but particularly the scalp, sacral area, and over the extensor aspect of the knees and elbows

• the major manifestation of psoriasis is the chronic skin disease (although psoriatic joint disease is another major morbidity associated with psoriasis)
• psoriatic skin disease is characterised by cutaneous inflammation and epidermal hyperproliferation (normally cells of the epidermal layer renew every 28 days, but in psoriasis the regeneration occurs every 2 to 4 days) (1,2)
  • lesions appear on any part of the skin, but particularly the scalp, lumbosacral area and over the extensor aspect of the knees and elbows (3).
    • Characteristically, there are:
      • well-defined, raised, erythematous and scaly lesions (3), which are "salmon pink" or "full rich red" in colour
      • surface silvery scale which may be easily removed often leading to pin - point capillary bleeding (Auspitz sign) (4)
      • they may or may not itch but this is not usually a prominent feature
• acute disease may manifest as inflammation and erythema while chronic lesions present as typical plaques (4). In most of the patients psoriasis presents in a chronic course with periods of remission (1).
• psoriasis is an emotionally and physically debilitating disease which is often underestimated by medical practitioners (4)

A strong genetic predisposition can be seen in psoriasis. Around 8 genetic susceptibility loci (PSORS I-VIII) have been observed (1). Psoriasis susceptibility 1 (PSORS1) locus located on the 6th chromosome is considered to be the most important one and can be seen in up to 50% of psoriasis cases (3).

NICE suggest (4):

• psoriasis is an inflammatory skin disease that typically follows a relapsing and remitting course - prevalence of psoriasis is estimated to be around 1.3-2.2% in the UK.
• is uncommon in children (0.71%) and the majority of cases occur before 35 years
  • is associated with joint disease in a significant proportion of patients (reported in one study at 13.8%)
  • plaque psoriasis is characterised by well-delineated red, scaly plaques that vary in extent from a few patches to generalised involvement
    • by far the most common form of the condition (about 90% of people with psoriasis)
    • other types of psoriasis include guttate psoriasis and pustular (localised or generalised) forms
  • distinctive nail changes occur in around 50% of all those affected and are more common in people with psoriatic arthritis
• several studies have also reported that people with psoriasis, particularly those with severe disease, may be at increased risk of cardiovascular disease, lymphoma and non-melanoma skin cancer
• therapeutics:
  • first-line therapy describes traditional topical therapies (such as corticosteroids, vitamin D and vitamin D analogues, dithranol and tar preparations)
  • second-line therapy includes the phototherapies (broad- or narrow-band ultraviolet B light and psoralen plus UVA light [PUVA]) and systemic non-biological agents such as ciclosporin, methotrexate and acitretin
  • third-line therapy refers to systemic biological therapies such as the tumour necrosis factor antagonists adalimumab, etanercept and infliximab, and the monoclonal antibody ustekinumab that targets interleukin-12 (IL-12) and IL-23

A useful summary algorithm based on NICE guidance for management of psoriasis in adults has been produced (5). This is an excellent summary for management in primary care:

Open Image in Modal

Open Image in Modal

Notes (5):

Key points when prescribing topical steroids:

• ointments should be used in the first instance if cosmetically acceptable. Creams contain more water and therefore may contain more preservatives - but they may be more cosmetically acceptable
• *there should be a four week gap between courses of potent/very potent steroid treatments
• refer to relevant product SPC (www.medicines.org.uk) for further information on side effects and excipients

References:

1. American Academy of Dermatology 2008. Guidelines of care for the management of psoriasis and psoriatic arthritis - Section 1. Overview of psoriasis and guidelines of care for the treatment of psoriasis with biologics
2. American Academy of Dermatology. Psoriasis
3. Schon M.P, Boehncke W.H. Psoriasis. NEJM 2005;352:1899-1912.
4. Guillen S, Khachemaoune A. Photo quiz - Large, Silvery Plaques. AFP 2007;75(8)
5. NICE (September 2017). Psoriasis - the assessment and management of psoriasis
6. NHS Bedfordshire Clinical Commissioning Group. Bedfordshire Psoriasis Summary Guidance - adults (Accessed 21/8/2019).