Psoriasis

Overview

Psoriasis is a common chronic inflammatory skin condition characterized by raised, red, itchy, scaly plaques on the skin. It is caused by an abnormal T-cell-mediated immune response. T-cells release cytokines which leads to keratinocyte proliferation.

10-15% of cases are associated with psoriatic arthritis. It affects 2-4% of the population. Can affect any age but has 2 peaks of incidence at 15-25 years and 50-60 years. The condition is usually life-long.

Types of psoriasis

Type	Description
Classical psoriasis (typical or chronic plaque)	90% of cases. Plaques are erythematous well-circumscribed with silver scaling. > 3cm in diameter. Associated with nail changes, pain, and itching (but less than dermatitis)
Guttate psoriasis (Raindrop lesions)	Occurs in the young following streptococcal tonsillitis (acute guttate psoriasis). Has multiple discoid erythematous and scaly macules and plaques on the trunk. Smaller plaques of < 3cm in diameter.
Palmoplantar pustular	Has yellow-brown pustules on palms and soles
Flexural (body folds)	Erythematous plaques without scales. Common in women, elderly, and HIV positive. Difficult to differentiate it from eczema and diagnose as psoriasis due to its unusual distribution (submammary, axillary, anogenital, umbilical)
Erythrodermic (total body redness)	Acute onset of erythroderma and pustular plaques. It is an emergency. Managed with Methotrexate.

• Risk factors for psoriasis
  • Genetic susceptibility
  • Smoking
  • Obesity
  • Psychological stressors
• Precipitating factors
  • Trauma (Koebner’s phenomenon)
  • Infection (Tonsillitis)
  • Beta-Blockers, Lithium, Antimalarials, NSAIDs, and ACEIs
  • Emotional stress
  • Sunlight
  • Puberty
  • Menopause
  • Alcohol
• Histopathology
  • Keratinocyte hyperproliferation (differentiation)
  • Parakeratosis (retained nuclei)
  • Acanthosis (thick epidermis)
  • Absent granular layer
  • Lengthened rete ridges
  • Thin dermal papillae
  • Dilated tortuous capillaries
  • munro’s micro-abscesses
  • T-cells in the upper dermis
• Common location of psoriasis Can affect any part of the body
  • Scalp especially behind the ears
  • Elbows
  • Knees
• Signs and symptoms
  • Symmetrical, erythematous plaques white/silver scaling often on extensor surfaces (front of knees, back of elbows)
  • Itching (accompanies by excoriation and lichenification in long-term more severe cases)
  • Auspitz sign (capillary bleeding on scale removal)
  • Nail changes (50%): pitting, onycholysis (nail lifting off the bed), subungual hyperkeratosis, Beaus’ lines (horizontal lines across the nails)
• Differential diagnosis of nail changes
  • Dermatitis (discoid or seborrhoeic)
  • Lichen planus
  • Pityriasis rosea (especially guttate psoriasis)
  • Secondary syphilis
  • Reiter’s syndrome (especially palmoplanar psoriasis)
  • Discoid lupus
  • Fungal infection
  • Alopecia areata
• Conditions associated with psoriasis
  • Psoriatic arthritis (onset within 10 years of onset of dermatological psoriasis, affects 13% of patients with psoriasis)
  • Inflammatory bowel disease
  • Uveitis
  • Coeliac disease
  • Type 2 Diabetes Mellitus, Hypertension, Hyperlipidaemia, and Gout
• Indications for referral to a dermatologist (specialist)
  • 10% of body surface area affected
  • Not responding to topical treatment
  • Psoriasis in children
  • Psoriasis having a major impact on psychological health
  • Associated mental illness e.g. Major Depressive Disorder, Anxiety secondary to their skin condition
• Complications of psoriasis
  • Erythroderma
  • Psychological and Social Effects

Treatment of Psoriasis

Typical Regimen for the treatment of psoriasis

Line	Treatment
1st line	Vitamine D analogues +/- topical steroids + tar/salicylic acid +/- UVB
2nd line	Retinoids, PUVA, UVB, Immunosuppressants
3rd line	Dithranol
Goekerman regimen	Tar + UVB
Ingram regimen	Goekerman + Dithranol

• Risk reduction (Lifestyle modification)
  • Smoking cessation
  • Reduce alcohol intake
  • Weight loss
  • Avoid long sunlight exposure
  • Manage stress (mental health)
• Topical agents used to treat psoriasis
  • Emollients
  • Corticosteroids (Betamethasone 0.1%, Hydrocortisone 1%)
  • Vitamin D analogues (Calcipotriol, tacalcitol, calcitriol)
  • Corticosteroids + Vitamin D analogs (Daivobet, Enstillar foam)
  • Coal tar preparations
  • Dithranol
  • Keratolytics (Salicylic acid)
  • Retinoids (Tazarotene)
• Systemic treatment of psoriasis
  • Phototherapy
    • UVB – classic and guttate psoriasis (Narrowband UVB has a low risk of burning and long-term sun damage) and is used before UVA
    • Photochemotherapy UVA (PUVA): used in combination with retinoids (to reduce the dose of PUVA) to treat cases not responsive to UVB. Associated with long-term skin damage and increased risk of cancer
  • Retinoids (Acitretin)
  • Immunosuppressants (Methotrexate, Cyclosporine, Azathioprine, Hydroxyurea)
  • Biological agents (Etanercept, adalimumab, infliximab)
• Prognosis
  • Psoriasis has a variable course and relapse is common
  • Poor prognostic factors include a strong family history and early age of onset
  • Over-use of steroids can cause pustular flares which can lead to serious systemic infections