Pustular psoriasis

Psoriasis is a chronic, non-contagious, autoimmune disease involving keratinocyte proliferation along with inflammation and angiogenesis. It is sometimes associated with arthritis, myopathy, enteropathy, spondiolytic joint disease or AIDS. It frequently affects skin of elbows, knees, scalp, lumbosacral areas, intergluteal cleft and glans penis. It is characterized by pink to salmon colored psoriatic plaques covered and demarcated by silver white scales.

Classification:

1. Guttate psoriasis: Is characterized by numerous small, scaly, red or pink, teardrop-shaped lesions. These numerous spots of psoriasis appear over large areas of the body, primarily the trunk, but also the limbs, and scalp. Guttate psoriasis frequently follows a streptococcal infection, typically streptococcal pharyngitis.

2. Nail psoriasis: Produces a variety of changes in the appearance of finger and toe nails. These changes include discolouring under the nail plate, pitting of the nails, lines going across the nails, thickening of the skin under the nail, and the loosening (onycholysis) and crumbling of the nail.

3. Plaque Psoriasis (Psoriasis Vulgaris): The common raised patch (plaque) variety.

4. Inverse Psoriasis (Flexural Psoriasis): Involves the body folds like axilla, groin, below the breasts and in between the buttocks.

5. Psoriatic arthritis: Involves joint and connective tissue inflammation. Psoriatic arthritis can affect any joint but is most common in the joints of the fingers and toes. This can result in a sausage-shaped swelling of the fingers and toes known as dactylitis. Psoriatic arthritis can also affect the hips, knees and spine (spondylitis). About 10-15% of people who have psoriasis also have psoriatic arthritis.

Pathogenesis:

1. Genetic factor (HLA C associated) / Provocating factors (Trauma, streptococcal infection, stress, smoking, drugs, endocrine)
2. Interaction of CD4+T cells with Antigen presenting cells (APCs) in skin
3. Activation of CD8+T cells in epidermis
4. Interaction of CD4+, CD8+ T cells, dendritic cells (APCs) and keratinocytes (T-lymphocyte mediated immune response)
5. Secretion of cytokines : IL-12, IFN-γ and TNF
6. Inflammation and proliferation of keratinocytes

Morphology:

1. Acanthosis with regular downward elongation of rete ridges
2. Elongation and edema of dermal papillae with broadening of their tips
3. Hyperkeratosis with parakeratosis
4. Suprapapillary thinning of stratum granulosum
5. Absence of granular cell layer
6. Auspitz sign (bleeding when scale is lifted from plaques)
7. Munro microabscesses: Neutrophils form small aggregates within the parakeratotic stratum corneum
8. Upper dermal vasculature shows dilatation and tortuosity

Treatments and drugs:

A. Topical:
Topical corticosteroids
Vitamin D analogues
Anthralin
Topical retinoids
Calceneurin inhibitors
Salicyclic acid
Coal tar
Moisturizers

B. Phototherapy

C. Oral or parenteral:
Methotreaxate
Cyclosporine
Retinoids
Hydroxyurea

Although doctors choose treatments based on the type and severity of psoriasis and the areas of skin affected, the traditional approach is to start with the mildest treatments i.e. topical creams and ultraviolet light therapy (phototherapy) and then progress to stronger ones if necessary.

Lecture Notes: Introduction, classification, pathogenesis, morphology, drugs and treatment of psoriasis

Reference:
a. Robbin’s Pathology
b. Harshamohan’s Pathology
c. Mayoclinic and Wikipedia

Tags: auspitz sign, munro microabscess, phototherapy, psoriasis, psoriatic arthritis, pustules

Last updated: September 2, 2010

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