-is a chronic non-infectious inflammatory dematosis characterized by well demarcated erythematous plaques topped by silvery scales.
Epidemiology
-1.5-3% of population in Europe and North America
-Sex incidence is equal
-Peak age: 20s, 30s and 60s.
-may start at any age but unusual in children <8 years.
Aetiopathogenesis
-Genetics:
-35% of patients show family history.
-if one parent affected, probability-25%
-if both parents affected, probability increases up to
60%
-Strongly correlates with HLA antigens, Cw6, B13 and B17.
-Epidermal kinetics and metabolism:
-epidermal cell proferation rate increased by 20 folds.
-epidermal cell turnover is reduced from 28 days to 4 days.
-Precipitating factors:
-Koebner phenomenon- trauma to epidermis and dermis such as a scratch or surgical scar can precipitate psoriasis.
-Infection- streptococcal sore throat infection--->Guttate psoriasis
-Drugs:
-beta blockers, lithium and antimalarials.
-Sunlight:
-aggravates psoriasis.
-Psychological stress:
-aggravates psoriasis.
Pathology
-epidermis is thickened with keratinocytes retaining their nuclei
-no granular layer but keratin builds up loosely at the horny layer
-rete ridges are elongated and polymorphs infiltrate up into the stratum corneum forming micro-abcesses.
-dilated capilaries.
(Mnemonics- easier to remember:
Pathogenesis:
HARP:
-Hyperkeratosis – thickening of cornified layer
-Acanthosis – epidermal thickening (3-5 times normal)
-Rete ridge elongation (arrowheads)
-Parakeratosis – retained nuclei in stratum corneum
STOP
-Subungual hyperkeratosis (proliferation under nail bed)
-Thickening
-Onycholysis (separation from the nail bed)
-Pitting, ridging
.
Other features:
-Absent granular layer and infiltration of neutrophils and activated lymphocytes (from dermis to epidermis)
*
PSORIASIS:
Pink Papules/ Plaques/ Pinpoint bleeding (Auspitz sign)/ Physical injury (Koebner phenomenon)/ Pain
Silver Scale/ Sharp margins
Onycholysis/ Oil spots
Rete Ridges with Regular elongation
Itching
Arthritis/ Abscess (Munro)
Stratum corneum with nuclei, neutrophils
Immunologic
Stratum granulosum absent/ Stratum Spinosum thickening
Clinical Features
1.Plaque
-well defined, disc-shaped plaques involving elbows, kness, scalp hair margin or sacrum
-usually red covered by waxy white scales
-2cm to more in diameter.
2.Guttate
-an acute symmetrical eruption of drop-like lesions usually on the trunk and limbs.
-especially in young person and may follow streptococcal infection.
3.Flexural
-affects axillae, sub-mammary areas and natal cleft
-plaques are often smooth and often glazed.
-mostly in elderly.
4.Localised manifestations
-Palmoplantar pustulosis:
-yellow to brown coloured sterile pustules on the palms or soles.
-common in females of cigarette smokers and middle aged persons.
-Acrodermatitis of Hallopeae:
-uncommon
-in digits and fingers
-Scalp psoriasis:
-may be the sole manifestation of the disease
-can be confused with dandruff but more thicker scaled and demarcated.
-Napkin Psoriasis:
-well-defined psoriasis forming eruptions in nappy areas of infants.
5.Generalised pustular
-rare and even life threatening.
-sheets of small, sterile yellowish pustules develop on an erythematous background.
-fever, malaise and acute.
6.Nail involvement:
-in 50% of the patients
-matrix or nail bed affected.
-Thimble pitting is the commonest change--->Onycholysis(separation of distal edge of nail from the nail bed)
-an oily or salman pink discolouration of the nail bed seen.
-subungual hyperkeratosis.
-frequently associated with psoriatic arthropathy.
Complications
1.Psoriatic Arthropathy development.
-in 5% of the patients.
-distal arthritis commonest pattern--->swelling of DIP joints--->sausage like fingers.
-Rheumatoid-like arthritis which is poly- and symmetrical.
2.Mutilans Arthritis
-associated with severe psoriasis
-erosions in small bones of hand and feet.
3.Ankylosing Spondylitis/Sacroiliitis
-These patients are usually positive for HLA-B27.
4.Erythroderma Psoriasis
-generalised exfoliative dermatitis defines any inflammatory dermatosis which nearly involves all the skin surfaces.
Management
1.Topical Therapy: -first line of treatment.
(i)Vitamin D analogues
-synthetics:
-Calcipotriol(Donovex)-100g/week as 40% of body surface on twice daily basis)-ointment/cream.
-Tacalcitol(Curatoderm)-35g/week as 20% " "............" )
*They inhibit cell proliferation and stimulate keratinocyte differentiation and correcting some of the epidermal cell turnover abnormalities in Psoriasis.
(ii)Topical Corticosteroids
-as creams, ointments and gels.
-As an advantage of being clean, non-irritant and easy to use.
-treatment of choice for face, genitalia and flexures and are good for stubborn plaques on hands and feet.
(iii)Coal Tar Preparations:
-Coal tar distillates used for decades.
-acts by inhibiting DNA synthesis.
-but smelly and messy.
-And good for chronic plaque psoriasis or guttate psoriasis once acute phase has past.
(iv)Dithranol(Anthralin):
-has anti-mitotic effect.
-irritant to normal skin
-cannot be used on face or genitalia as it stains skin,hair, linen, clothes, etc.
Therefore, surrounding area is protected with a bland preparation such as white soft paraffin was and treated area is covered with tube gauze.
(v)Retinoids:
-Tazarotene
-effective for chronic plaque psoriasis
(vi)Keratolytics and Scalp preparations:
-for hyperkeratotic psoriasis
-5% salicyclic acid ointment.
2.Systemic Therapy.
-for life threatening and unresponsive to topical treatment.
-phototherapy and photochemotherapy.
(i)Methotrexate:
-the folate antagonist methotrexate is well-established as an effective for severe psoriasis and may have anti-inflammatory as well as immunomodulatory effect.
-given once a week orally as a single dose.(7.5-15mg)
-is teratogen
-Contraindications:
-liver disease
-acute infections
-alcoholism
(ii)Retinoids:(as Re-PUVA)
-Vit A derivative- Acitretin(as Neostigason capsule)
-particularly effective in treating pustular psoriasis and thinning hyperkeratotic plques.
-serious effects includes hyperstosis, abnormal liver function, hyperlipidaemia and teratogenicity.
(iii)Ciclosporin:
-an immunosuppressant(widely used to prevent rejection of organ transplants)
-effective in severe psoriasis.
-acts by inhibiting T-lymphocytes activation and IL-2 production.
-side effects include reversible dose-dependent nephrotoxicity, risk of skin cancer or lymphoma and concomittant UV treatment is avoided.
(iv)Others:
-other cytotoxic or immunosuppressive drugs control psoriasis but not as potent as methotrexate.
-Hydroxyurea
-do not affect liver but causes bone marrow suppression.
-Azathioprine
-is both hepatotoxic and myelosuppressive.
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