Psoriasis

Introduction | Aetiology and Risk Factors | Clinical Presentation | Diagnosis | Management and Treatment | Prevention | When to Refer | References

Introduction

Psoriasis is a chronic inflammatory skin condition characterised by well-demarcated, erythematous plaques with overlying silvery scale. It is a multifactorial disease influenced by genetic, environmental, and immune-mediated factors. Psoriasis can significantly impact quality of life due to its visibility and symptoms, which may include itching and discomfort.

Aetiology and Risk Factors

Psoriasis is believed to result from an interaction between genetic predisposition and environmental triggers, leading to an abnormal immune response:

• Genetics: A family history of psoriasis increases the risk, with certain HLA genes implicated.
• Environmental Triggers: Factors such as stress, infections (e.g., streptococcal throat infection), skin trauma (Koebner phenomenon), and medications (e.g., beta-blockers, lithium) can trigger or exacerbate psoriasis.
• Immune System: Psoriasis is an immune-mediated condition, with T-cells playing a central role in driving inflammation and keratinocyte proliferation.
• Lifestyle Factors: Smoking, alcohol consumption, and obesity are associated with an increased risk and severity of psoriasis.

Clinical Presentation

Psoriasis presents with various clinical features depending on the type and location of the lesions:

1. Trunk & Limbs

• Clinical Features: Well-defined symmetrical small and large scaly plaques, predominantly on extensor surfaces but can be generalised.
• Treatment:
  • Calcipotriol/Betamethasone (Dovobet, Enstilar) combination product should be used first line, once daily until lesions flatten.
  • If the response is sub-optimal at 8-12 weeks, review adherence.

2. Scalp Psoriasis

• Clinical Features: Often more common than appreciated and easier felt than seen. May be patchy, socially embarrassing, and typically extends just beyond the hairline.
• Treatment:
  • Descale if necessary with coconut oil or, if more severe, Sebco Ointment – massaged onto the scalp and ideally left overnight. Wash out with Capasal. Continue to use until the scale becomes much thinner.
  • Treat ongoing inflammation with potent topical steroids such as Synalar Gel or Diprosalic scalp application applied at night, also Dovobet Gel or Enstilar foam could be used.
  • Maintenance therapy: Once or twice weekly tar-based shampoo such as Capasal, with once or twice weekly potent topical steroids. If the scale thickens, then revert to Sebco ointment as neeeded.

3. Flexures & Genitalia

• Clinical Features: Erythematous patches, shiny red, and lack scale. Commonly mistaken for candidiasis.
• Treatment:
  • Mild or moderate topical steroid, such as Daktacort, 1% hydrocortisone, or eumovate once daily. For thicker plaques, consider a short course of Trimovate for a week to gain control, then wean down to a moderate or mild topical steroid.
  • A topical vitamin D preparation such as Silkis or Curatoderm can be used on the opposite end of the day to the topical steroid and continued daily while using the steroid twice a week to keep control.
  • For flexures, topical calcineurin inhibitors can be used instead of topical steroids or vitamin D analogs, but avoid using these agents in uncircumcised male patients unless directed by secondary care.

4. Face

• Clinical Features: An uncommon and distressing site, sometimes with plaques but more often similar to that seen in seborrhoeic dermatitis.
• Treatment:
  • Eumovate Ointment – many would use this initially, for a week, and follow on with any of:
  • Tacrolimus 0.1% ointment – once or twice a day and reducing with response (note this need dermatology input).
  • Silkis ointment – can cause irritation, so introduce gradually (initially twice a week, then build up to daily).
  • Daktocort cream once or twice a day for more seborrhoeic types.

5. Guttate Psoriasis

• Clinical Features: Rapid onset of very small ‘raindrop like’ plaques, mostly on the torso and limbs, usually following a streptococcal infection. May lack scale initially.
• Treatment:
  • Refer to secondary care for light therapy.
  • In the interim, consider treating with tar lotion (Exorex lotion) 2-3 times a day, or using topical steroids such as eumovate, Dovobet or Enstilar foam for itchy patches.

6. Palmoplantar Pustular Psoriasis

• Clinical Features: Very resistant and difficult to treat. Creamy sterile pustules mature into brown macules.
• Treatment:
  • This is more likely in smokers: strongly advise stopping smoking.
  • Dermovate Ointment at night.
  • A moisturiser of choice to be used through the day.

7. Nails

• Clinical Features: In about 50% of patients, pitting, hyperkeratosis, and onycholysis. NB. Look for arthritis and co-existing fungal infection. Terbinafine may aggravate psoriasis.
• Treatment:
  • Practical tips – keep nails short, use nail buffers.
  • Nail varnish and gel are safe to use.

8. Psoriatic Arthritis

• Clinical Features: Inflammatory polyarthritis, spondylarthritis, synovitis, dactylitis, and tendonitis.
• Treatment:
  • Psoriatic arthritis is under-recognized, and it is very important it is diagnosed and referred early to Rheumatology because of the risk of permanent joint destruction and functional damage.

Diagnosis

Psoriasis is primarily diagnosed clinically based on its characteristic appearance and distribution:

• Physical Examination: Look for well-demarcated, erythematous plaques with silvery scale, typically on extensor surfaces, scalp, and lower back.
• History: Assess for triggering factors, family history, and the presence of joint pain or stiffness, which may suggest psoriatic arthritis.
• Biopsy: Rarely required but may be performed if the diagnosis is uncertain.

When to Refer

Referral to a dermatologist or rheumatologist is recommended in the following situations:

• Severe or Extensive Disease: When topical treatments are ineffective or if the psoriasis is widespread.
• Palmoplantar Pustular Psoriasis: Due to its resistance to treatment and significant impact on quality of life.
• Psoriatic Arthritis: Urgent referral to rheumatology is necessary to prevent joint damage.
• Diagnostic Uncertainty: If the diagnosis is unclear or other conditions are suspected.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Psoriasis. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Psoriasis: Diagnosis and Management. Available at: https://www.nice.org.uk/guidance/ng200 (Accessed: 26 August 2024).
3. British National Formulary (2024) Topical and Systemic Treatments for Dermatological Conditions. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).
4. Primary Care Dermatology Society (2019) Psoriasis Treatment. Available at: https://www.pcds.org.uk/files/general/Psoriasis_Treatment_2019-web.pdf (Accessed: 26 August 2024).