Psoriasis

Definition
                -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.
                                 

                                                               




0 comments:

Post a Comment