GP- Derm Flashcards
Psoriasis: pathophysiology including gene associations
- multifactorial and not yet fully understood
- genetic: associated HLA-B13, -B17, and -Cw6. Strong concordance (70%) in identical twins
- immunological: abnormal T cell activity stimulates keratinocyte proliferation. There is increasing evidence this may be mediated by a novel group of T helper cells producing IL-17, designated Th17. These cells seem to be a third T-effector cell subset in addition to Th1 and Th2
- 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
recognised subtypes of psoriasis and how they present
- plaque psoriasis: the most common sub-type resulting in the typical well-demarcated red, scaly patches affecting the extensor surfaces, sacrum and scalp
- flexural psoriasis: in contrast to plaque psoriasis the skin is smooth
- guttate psoriasis: transient psoriatic rash frequently triggered by a streptococcal infection. Multiple red, teardrop lesions appear on the body
- pustular psoriasis: commonly occurs on the palms and soles
other features of psoriasis
nail signs:
pitting
onycholysis (separation of the nail from the nail bed)
subungual hyperkeratosis
loss of the nail
arthritis
complications of psoriasis
- psoriatic arthropathy (around 10%)
- increased incidence of metabolic syndrome
- increased incidence of cardiovascular disease
- increased incidence of venous thromboembolism
- psychological distress
Psoriasis exacerbating fators
- trauma
- alcohol
- drugs: beta blockers, lithium, antimalarials (chloroquine and hydroxychloroquine), NSAIDs and ACE inhibitors, infliximab
- withdrawal of systemic steroids
- Streptococcal infection may trigger guttate psoriasis.
Chronic plaque psoriasis features
Chronic plaque psoriasis is the most common form of psoriasis seen in clinical practice, accounting for around 80% of presentations.
Features
* erythematous plaques covered with a silvery-white scale
* typically on the extensor surfaces such as the elbows and knees. Also common on the scalp, trunk, buttocks and periumbilical area
* clear delineation between normal and affected skin
* plaques typically range from 1 to 10 cm in size
* if the scale is removed, a red membrane with pinpoint bleeding points may be seen (Auspitz’s sign)
Guttate psoriasis presentation and features
Guttate psoriasis is more common in children and adolescents. It may be precipitated by a streptococcal infection 2-4 weeks prior to the lesions appearing.
Features
* tear drop papules on the trunk and limbs
* gutta is Latin for drop
* pink, scaly patches or plques of psoriasis
* tends to be acute onset over days
management of guttate psoriasis
Management
* most cases resolve spontaneously within 2-3 months
* there is no firm evidence to support the use of antibiotics to eradicate streptococcal infection
* topical agents as per psoriasis
* UVB phototherapy
* tonsillectomy may be necessary with recurrent episodes
Differentiating guttate psoriasis and pityriasis rosea
chronic plaque psoriasis management
- Calcipotriol + betamethasone (Dobovet)
- Tar
- Dithranol
- Tacalcitol once daily before bed and only for 12 week courses
secondary management of chronic plaque psoriasis
Phototherapy
* narrowband ultraviolet B light is now the treatment of choice. If possible this should be given 3 times a week
* photochemotherapy is also used - psoralen + ultraviolet A light (PUVA)
* adverse effects: skin ageing, squamous cell cancer (not melanoma)
Systemic therapy
* oral methotrexate is used first-line. It is particularly useful if there is associated joint disease
* ciclosporin
* systemic retinoids
* biological agents: infliximab, etanercept and adalimumab
* ustekinumab (IL-12 and IL-23 blocker) is showing promise in early trials
scalp psoriasis management
- NICE recommend the use of potent topical corticosteroids used once daily for 4 weeks
- if no improvement after 4 weeks then either use a different formulation of the potent corticosteroid (for example, a shampoo or mousse) and/or a topical agents to remove adherent scale (for example, agents containing salicylic acid, emollients and oils) before application of the potent corticosteroid
Face, flexural and genital psoriasis management
NICE recommend offering a mild or moderate potency corticosteroid applied once or twice daily for a maximum of 2 weeks
Topical corticosteroids side effects and maximum time they should be used in psoriasis depending on strength
Vitamin D analogues examples, mode of action and how they should be used
