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  1. Introduction
    A common, chronic, disfiguring, inflammatory and proliferative condition of the skin, in which both genetic and environmental influences have a critical role.

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Fig-1.The ‘salmon pink’ colour of psoriatic lesions.


The most characteristic lesions consist of red, scaly, sharply demarcated, indurated plaques, present particularly over extensor surfaces(tip of elbows ,knees) scalp and sacral area.

  1. Prevalence = 2%
  2. Type I- Age of onset at or below 40 yrs (75%)
  3. Type II- Age of onset above 40 yrs (25%)

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Fig-2. Auspitz’s sign: removal of the thinned suprapillary epidermis, by gentle scraping, reveals vascular bleeding points.

  1. Clinical Feature
    1. Psoriasis is a chronic erythemato-squamous condition characterized by sharply circumscribed salmon pink  plaques covered with silvery scales.
      1. Non-pustular psoriasis
      2. Pustular psoriasis
      3. Psoriasis with arthropathy. They can be subclassified further into:
  2. Non-pustular Psoriasis
    1. Chronic Plague type
      1. Acute Guttate
      2. Inverse/flexural
      3. Erythrodermic
      4. Regional: Scalp, palms & soles, nails
      5. Unstable nummular
      6. Sebo-psoriasis
    2. Rupioid, elephantine and ostraceous
  1. Pustular Psoriasis
    1. Localized pustular psoriasis:
      1. Palmoplantar pustulosis
      2. Acrodermatitis continua
    2. Generalized pustular psoriasis:
      1. Acute generalised pustular psoriasis(Von Zumbusch)
      2. Pustular psoriasis of pregnancy(Impetigo herpetiformis)
      3. Infantile and juvenile
      4. Circinate
      5. Localized (not hands and feet).

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Fig-3.Pustualar Ps- Discrete tiny pustules over the background of erythema

  1. Psoriasis with Arthropathy
    Psoriasis with arthropathy- occurs in 10-15% of those with psoriasis

  1. Moll And Wright Classification
    1. 5 Types of arthropathy found:
      1. Oligoarticular asymmetrical arthritis, (Most common)
      2. Symmetrical involving small joints of fingers likes rheumatoid arthritis,
      3. Classical distal arthropathy involving distal interphalangeal joints, (Classical)
      4. Destructive arthritis mutilans
      5. Psoriatic spondyloarthropathy which is similar to ankylosing spondylitis.

Two interesting phenomena occur in Psoriasis. They are mutually exclusive:


Koebner and reverse Koebner responses. Any form of trauma may result in psoriasis appearing in the traumatized areas which is known as Koebner phenomenon or isomorphic response. A degree of healing may occur when a psoriatic plaque is traumatized which is the reverse Koebner phenomenon. It also explains why some patient found cryotherapy is useful to suppress psoriasis.

  1. The commonest form of psoriasis is the chronic plaque type which usually presents as brightly erythematous scaly plaques at the predisposed areas i.e. the extensor aspect, the tip of elbows, knees, sacral area, the scalp.
  2. They may be associated with no symptoms to moderate pruritus. Excessive dandruff and scaling from the lesional area may be an early complaint.
  3. Family history is not very commonly found in this group because the other family members may not have the disease at all or if possess, usually in a very mild degree.
  4. Patient may have history of acute guttate psoriasis before but it either never clears or reappears as plaque form.
  5. The most useful form to confirm the diagnosis is to use the wooden spatula to scrape the surface of the suspected lesion, profuse silvery scaling can easily be generated
  6. Grattage test- scraping the surface of lesion produces silvery scaling
  7. Guttate= Coin like
  8. Acute guttate psoriasis often preceded by a history of sore throat 10 days to 2 weeks ago.
  9. It may be a streptococcal infection.
  10. The small guttate maculopapular scaly lesion still have the characteristic feature of psoriasis and hence there will be no diagnostic problem.
  11. Occasionally, pityriasis rosea, pityriasis lichenoides have to be excluded.
  12. The course of the disease initially will go into remission in few months time but it can reappear after another attack of infection and many do gradually become a chronic plaque type case.
  13. Localized pustular
  14. Localized pustular psoriasis of palms and soles usually present as symmetrical, monomorphic eruption of small sterile pustular eruption on hands and feet.
  15. They are painful rather than pruritic. Very often, brownish thick wall pustules are found.
  16. They are resistant to treatment and will be quite disabling. Another form of local pustular psoriasis is asymmetrical involvement affecting distal phalanx with nail destruction. It is called acrodermatitis continua of Hallopeau.
  17. It may change to generalized pustular form.
  18. Smoking have proven adverse effects on localised pustular psoriasis of palms and soles
  19. Generalized pustular psoriasis can present in a psoriatic prone patient who is given systemic steroid for other conditions and upon sudden withdrawal of the steroid, generalized pustular psoriasis will be precipitated for the first time.
  20. Occasionally, it develops from the unstable nummular psoriasis or acrodermatitis continua after inappropriate irritant therapy or withdrawal of extensive topical steroid. Pregnancy can sometimes associate with the generalized pustular psoriasis.
  21. There are low grade fever, pain and burning sensation over the pustules.
  22. Systemic and constitutional upset may be severe. This requires in-patient management with bed-rest and institution of transient systemic therapy.
    • Acitretin (retinoids) are DOC in pustular psoriasis.
  1. Nail Involvement is commonly seen in all types of psoriasis which can affect the nail matrix and nail bed leading to pitting, discoloration, subungual hyperkeratosis, onycholysis, splinter hemorrhage.
  2. Circular area of discoloration of nail bed resembling an oil drop underneath the nail - oil drop sign is most characteristic for psoriatic nail.
    1. Nail changes in psoriasis-
      1. Most common – Pitting
      2. Most characteristic – Oil drop sign

Patients with AIDS develop severe recalcitrant form of psoriasis.


The use of etretinate and anti-viral therapy such as zidovudine are necessary to control this type of psoriasis. (Retinoids)

Nail changes in Psoriasis 
•  Thimble pitting
•  Oil spots
•  Leukonychia
•  Ridging    
•  Onycholysis
•  Trachyonychia
•  Nail plate thickening
•  Yellow brown discoloration
•  Serial transverse depression
•  Longitudinal ridging
•  Subungual hyperkeratosis

  1. Pathophysiology of psoriasis
    1. Results from an interaction between an individual’s genetic susceptibility and specific environmental factors.
    2. PSORS1 gene (35-50% of heritability) has been mapped very near to HLA-Cw6 within the major histocompatibility complex.
    3. This region also encompasses the gene encoding TNF- α.
    4. Polymorphisms in the TNF-α promoter region, in conjunction with HLA-Cw6, influence the disease course, for example, the age at onset.
    5. A strong relationship between increased risk of psoriasis and polymorphisms at alleles for IL-12B and IL-23 receptor has been observed.
    6. After a triggering event, the Th1 cells and APCs interact to produce the ‘immunological synapse’.
    7. T-cell activation initiates the release of cytokines [including TNF- α, IFN-gamma, IL-12, IL-23 and IL-15], chemokines and growth factors resulting in keratinocyte proliferation, altered differentiation, angiogenesis and further recruitment of inflammatory cells.
    8. IL-23 leads to the development of Th17 cells.
    9. Th17 cells produce TNF- α, IL-17 and IL-22, the latter of which is believed to drive many of the epidermal changes in psoriasis.

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