Psoriasis Flashcards
What is Psoriasis ?
- It is a chronic inflammatory skin condition characterised by clearly defined, red and scaly plaques (thickened skin).
- It has a chronic, relapsing and remitting course
- It is classified into several subtypes
Who most commonly gets Psoriasis ?
- Can affect any age group but prevelence peaks in the 2nd and 5th decades of life
- Caucasians most commonly get it
- 1/3rd of patients with psoriasis have family members with psoriasis
What is the cause of psoriasis ?
The cause of psoriasis is multifactorial and not yet fully understood factors contributing include:
- Genetics: psoriasis prevelence is higher in people with these human leucocyte antigens - HLA-B13, -B17, & -Cw6.
- Immunological: abnormal T cell activity stimulates hyperproliferation of epidermal cells (e.g. keratinocytes). This may be mediated by T helper cells (Th17) producing IL-17. This results in increased number of cells entering cell cycle from the basal layer and a faster epidermal turnover time.
- Environmental: it is recognised that psoriasis may be worsened (e.g. Skin trauma, stress), triggered (e.g. Streptococcal infection) or improved (e.g. Sunlight) by environmental factors
What are the histological features of psoriasis ?
- Hyperkeratosis
- Parakeratotic stratum corneum (contains nuclei – normally none)
- Absence of granular layer
- Expanded prickle cell layer
- Rete ridge elongation
- Large capillary vessels in papillary dermis
- Leucocytes – Munro microabscesses in stratum corneum
List some of the precipitating environmental factors for psoriasis ?
- Emotional Stress
- Infection – strep throat and guttate psoriasis
- Drugs – Beta-blockers, lithium, anti-malarials, withdrawal of topical or systemic steroids
- Alcohol
- Trauma – Koebner phenomenon
- Smoking
- HIV / AIDS
- ( Ultraviolet irradiation – in 10% it worsens)
What is Koebner phenomenom ?
This is where psoriasis develops in sites of trauma 2-6weeks after the trauma is sustained. Examples of trauma it may devleop in include:
- Scratches
- Burns ( & sunburn)
- Other dermatoses e.g. contact dermatitis
- Surgical trauma
What is the typical distribution of psoriasis ?
The most common sites are scalp, elbows and knees, but any part of the skin can be involved.
What are the clinical features of psoriasis ?
- Usually 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 and they may have a moist peeling surface.
- Itch is usually mild but can be severe leading to scratching and lichenification.
- Painful skin cracks or fissures may occur.
- When psoriatic plaques clear up, they may leave brown or pale marks that can be expected to fade over several months.
List the main sub-types of psoriasis
- Guttate psoriasis
- Chronic plaque psoriasis
- Scalp psoriasis
- Flexural psoriasis
- Palmoplantar psoriasis
- Nail psoriasis
- Psoriatic arthritis
- Generalised pustulosis
- Localised palmoplantar pustulosis
Describe the appearance of chronic plaque psoriasis
- It presents as small to large, well-demarcated, erythematous scaly and thickened plaques.
- Plaques are palpable, raised with silvery scale
- Auspitz’ sign seen = removing scale reveals pin-point bleeding
- May develop due to Koebner phenomenon
- It most likely to affect extensor aspects of knees, elbows & sacrum
- It is often accompanied by scalp and nail psoriasis
What are the typical clinical features of guttate psoriasis ?
- Characterised by multiple small scaly plaques on the trunk and limbs. Looks like a shower of red, scaly teardrops that have fallen down on the body.
- Usually occurs following a streptococcal infection of the throat or an upper respiratory tract viral infection.
- Typically affects children & young adults (15-25)
What are the clinical features of scalp psoriasis ?
- Characterised by red scaly thickened patches (plaques). It often affects the scalp, may extend slightly beyond hairline.
- Scale is often silvery white
- Can cause severe dandruff due to falking of the skin
- May be very itchy
- The back of the head is a common site for psoriasis, but multiple discrete areas of the scalp or the whole scalp may be affected.
- May occur in isolation or with any other form of psoriasis.
What are the clinical features of flexural psoriasis ?
- Affects skin folds & genitals
- Due to the moist nature of the skin folds it presents differently. It tends not to have silvery scale, but is shiny and smooth.
- There may be a crack (fissure) in the depth of the skin crease.
- The deep red colour and well-defined borders characteristic of psoriasis may still be obvious.
- Scaly plaques may sometimes occur
What are the clinical features palmoplantar psoriasis ?
- Well-circumscribed, red, scaly, plaques similar to psoriasis elsewhere
- Can be painful / disabling
- Often very thick hyperkeratosis
What are the clinical features of erythrodermic psoriasis ?
- It is rare but occurs in the setting of known worsening or unstable psoriasis
- Features are of red dry skin all over the body (> 90%)
- Causes include – withdrawal of potent topical or systemic steroids, drug reactions, ultraviolet burns etc
What complications can develop as a result of erythrodermic psoriasis ?
- Hypothermia
- Cardiogenic shock
- Dehydration
- Anaemia
- Hypoproteinaemia
It is very serious and can be a fatal condition
What are the clinical features of nail psoriasis ?
Nail psoriasis can affect any part of one or more nails. There are often scaly plaques on the dorsum of the hands and fingers due to associated plaque psoriasis.
Psoratic nail changes include:
- Nail pitting
- Onycholysis = separation of the nail plate from the underlying nail bed
- Leukonychia = areas of white on the nail plate
- “oil-drop” lesions = a translucent yellow-red discolouration in the nail bed
- Sub-ungal hyperkeratosis = scaling under the nail
- Nail deformity
What psoriatic nail changes are shown in this pic ?
Leukonychia & Nail pitting
What are the clinical features of psoriatic arthritis ?
- Symptoms include joint pain, swelling and stiffness.
- Psoriatic arthritis is a painful, inflammatory condition of the joints that can occur in up to 30 per cent of patients with psoriasis.
- Large and small joints may be affected.
What are the 5 main patterns of psoriatic arthritis ?
- Asymmetric oligoarthritis (60-70%)
- Symmetrical polyarthritis (15%)
- Distal phalangeal joint disease (5%)
- Destructive arthritis (arthritis mutilans – 5%)
- Axial arthritis (5%) (spondylitis / sacroiliitis)
Oligoarthritis = affecting 2-4 joints
Polyarthritis = affecting ≥ 4 joints
What are the clinical features of generalised pustular psoriasis ?
- Generalised pustular psoriasis is characterised by recurrent acute flares.
- It presents with widespread sterile pustules on a background of red and tender skin
- Associated symptoms of Painful skin, fever, malaise
- May develop Hypoalbuminaemia, hypocalcaemia and leucocytosis, liver failure, acute renal tubular necrosis. Can be fatal.
- Causes include – withdrawal of steroids, infection, pregnancy, hypocalcaemia
What is palmoplantar pustulosis ?
- A chronic pustular condition affecting the palms and soles
- It is related to psoriasis and patients who develop it may also have lesions of psoriasis elsewhere
What are the clinical features of palmoplantar pustulosis ?
- Presents as crops of sterile yellow pustules occurring on one or both hands and feet.
- They are associated with thickened, scaly, red skin that easily develops painful cracks (fissures).
- Strong association with cigarette smoking & usually occurs in older people (>50)
How is psoriasis diagnosed ?
Clinically
What are the main problems with dithranol?
- Burns normal skin
- Stains clothing and bedding purple
What are the potential acute & chronic side effects of phototherapy used in the treatment of psoriasis ?
Acute:
- Erythema
- Blistering
- Photoconjunctivitis
- Exacerbation of Herpes Simplex
Chronic:
- Photoageing
- Photocarcinogenesis
Label the following nail signs and name the condition that all these nail signs are associated with ?
