Medicinus – Cours de Médecine en ligne


(Last Updated On: 10 March 2020)


Pathogenesis remains poorly understudged:

– Psoriasis is characterized by an acceleration of epidermal renewal

Turn over normal epidermal is 30 days

In psoriasis only 7 days

– this is related to immune disorders

– activation of LT – secretion of different cytokines (TNF Alpha, IL12, IL23 …)

– causing a psoriatic inflammatory reaction

responsible for the increased proliferation of keratinocytes

It is a “multifactorial” condition – genetic factors

30% of psoriatics are family-friendly

Childhood psoriasis is frequently linked to histocompatibility antigens (HLA-Cw6) – environmental factors

Alcohol and tobacco: TRT resistance factors

Infections: especially in childhood psoriasis flare-ups

Psychological factors and medications (lithium salt, beta blockers, IEC, CTC …) can induce or aggravate psoriasis


Elemental injury: rounded and well-restricted erythematoscaly plaque. – superficial scaly layer

A- The dander on the surface:

Color: white and dull, sometimes musky – Surface: smooth or rough

These dander are dry, of varying size and thickness

– may completely or partially mask the rash

Bleaching sign

Sign of candle stain

– Sign of the sticky film.

Pulling off a deepshot adhesive film

Sign of bloody dew or sign of AUSPITZ:

Appearance of fine hemorrhagic goutlets (naked dermal taste buds)

B- Erythema is underlying:

– located under the scaly layer

Characteristic pink colour, cogenty red (infs)

Disappears at the pressure press. – smooth and dry surface

no pain, no infiltration, no pruritus.

C Grouping and topography:


– Variable,

– rarely isolated plaque psoriasis,

– usually multiple or diffuse


punctiform “punctata” or in “guttata” drops a few mm in diameter

Nummular (nummulus-coin) a few cm in diameter

Plate: more or less geometric or circumcised contours occupying large areas

Universalis: widespread that affects almost the entirety of the


– very evocative of the diagnosis

At the beginning and throughout the duration of the disease; friction zones:

elbows, knees, forearm headboards, tibial regions, sacred region, palms and plants, scalp (refuge area or bastion).

Functional signs (pruriit): Psoriasis is little or not pruriginous


A- Depending on the seat:

1- Clasic forms: bastion:

2- Psoriasis of folds: Psoriasis inverted.

– glossy red plate and smooth little or no flaking

– seat: interfessier folds – inguinaux – genital regions – under breasts – axillary hollow

– Macerated, wet areas; michael rash.

Two differential diagnoses: eczema and fungus.

3- Scalp psoriasis:

– erythemato-scaly patch of very limited variable sizes covered with large dry dander crossed by the hair (non-afreeciant) – real shell covering the entire scalp

4- Nail psoriasis: 30-50% of cases

– sometimes isolated,

– Appearance of depression punctuated cupiliforms (nail in dice to sew)

– onycholysis with distal detachment

– hyperkeratosis under ungueal

– leuconychia

5- Psoriasis of palms and plants:

– often bilateral – a keratodermy in ilots or diffuse

Two differential diagnoses:

6- Facial psoriasis:

Rare, it can take on the appearance of seborrheic dermatitis (sebopsoriasis)

7- psoriasis of the mucous membranes:

– On the language:

Geographical language especially in pustular psoriasis

Scrotal language

– On the acorn: very limited spots, purely erythematous

B- Depending on age:

– may be early: psoriasis of the langes (napkin psoriasis)

– in children: often acute in drops and can follow a rhino-pharyngeal infection The face is more often affected than in adults

C- Psoriasis caused:

– Drugs: they may induce or aggravate psoriasis or be responsible for TRT resistance (lithium salts, beta-blockers, INF alpha) – koebner phenomenon: characterized by the appearance of psoriasis lesions on a skin trauma: streaks of scratching, surgical scars …

D- Serious forms:

1- Pustular Psoriasis:

2- Erythrodermic Psoriasis:

3- Arthropathe psoriasis:



A- Positive diagnosis:

1- Clinic:

2- Histology in case of diagnostic doubt:

a)- Epidermis:

b)- Derme:

c)– Hypoderma and annexes: No changes

B- Differential diagnosis:

  1. Microbial eczema.
  2. Epidermo-mycses.
  3. Lichen plan: very pruriginous papulo-squamous dermatosis also reaching the mucous membranes.
  4. Hematoma (associated lymphoma).


A- Limited Psoriasis:

1- Keratolytics:

2- Gearboxes:

B- Extended Psoriasis:

C- Severe Psoriasis: Extended or Rebellious:

D- Arthropathic Psoriasis:

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