Contact Dermatitis and Psoriasis Flashcards
Major commonality between contact dermatitis and psoriasis
Both T cell mediated!
Phases of contact dermatitis
- Sensitization (10-15 day duration)
- Elicitation (stimulated by rechallenge)
Spongiotic inflammation
Characteristic of contact dermatitis
Allergic Contact Dermatitis
An adverse cutaneous inflammatory reaction caused by contact with a specific exogenous allergen to which a person has developed allergic sensitization. Comprise 20% of all contact dermatitis.
Irritant Contact Dermatitis
An adverse cutaneous inflammatory reaction that occurs without sensitization, in direct proportion to the quantity/concentration and amount of exposure to the irritant exposure. Comprise 80% of all contact dermatitis.
Classic presentation of allergic contact dermatitis
pruritic, eczematous dermatitis initially localized to the primary site of allergen exposure
urushiol
Sensitizing substance for contact dermatitis in plants (like poison ivy). Released when plants are burned. Leads to more severe eruption on large swaths of body.
Subacute to chronic allergic contact dermatitis presentation
- erythema
- scaly juicy papules
- fissuring
- lichenification
- pruritis
- may present as a line or streak suggestive of physical contact
Important allergen classes in contact dermatitis
- Metals
- Topical medications
- Fragrances/dyes
- Preservatives
- Plants
The most commonly diagnosed cause of allergic contact dermatitis
Nickel
History taking for acute contact dermatitis
- Detailed history of usage of personal care products
- Investigation of hobbies, especially hiking
- Investigation of occupation (those requiring frequent hand washing, glove use, or frequent chemical exposure are most suspicious)
Clinical pearls for contact dermatitis
- Should be suspected in any eczematous-appearing eruption
- Not always bilateral even when antigen exposure is bilateral
- Even when contact is uniform, lesions are often patchy
- Can and does affect palms and soles (while many dermatitis-causing diseases do not)
- Distribution of lesions on skin may give a clue to how it came into contact with the offending substance
The gold standard for the diagnosis of allergic contact dermatitis
patch testing!!!
Treatment of allergic contact dermatitis
- Strategy for avoiding antigen, usually involving substitution of items or behaviors
- Topical corticosteroids first line treatment for short-term (Corticosteroid allergy
should be considered when an eruption persists, changes, spreads, or worsens following the use of steroids) - topical calcineurin inhibitors (tacrolimus, etc)
- For severe ACD, courses of oral corticosteroids are often given with a slow taper
Psoriasis is a prototypic ___-mediated autoimmune inflammatory skin disease
Psoriasis is a prototypic T resident memory cell-mediated autoimmune inflammatory skin disease
Main cytokine driver of psoriasis
IL-17
Under baseline conditions, ___ live next to___ in the skin that probably express the autoantigen they are specific for.
Under baseline conditions, resident autoreactive T cells live next to antigen presenting cells in the skin that probably express the autoantigen they are specific for.
Psoriatic skin lesions become induced when damage to the skin, infection or any other stimulus that leads to . . .
Psoriatic skin lesions become induced when damage to the skin, infection or any other stimulus that leads to dendritic cell activation, up regulates costimulatory molecules on antigen presenting cells and this causes the proliferation of autoreactive T cells in the skin.
Psoriatic inflammation
Psoriatic lesions on H and E
- hyperkeratotic and parakeratotic scale of the startum corneum
- elongation of the rete ridges of the epidermis with focal neutrophilic collections
- thinning of the suprapapillary epidermis
- dilated superficial dermal blood vessels (from angiogenic factors)
Psoriasis epidemiology
- 2% of individuals in US
- No anatomical sex preference
- Appears >30 years of age, often in teen years
- HLA-Cw6 haplotype associated with early onset and family history
__% of psoriatic individuals go on to develop psoriatic arthritis
30% of psoriatic individuals go on to develop psoriatic arthritis
rates of ___ and ___ are dramatically lower in individuals with psoriasis
rates of atopic dermatitis and allergic contact dermatitis are dramatically lower in individuals with psoriasis
Clinical description of psoriasis
- Lesions are well-demarkated, erythematous-pinkish, raised plaques with a white-silver scaly surface
- Vary in size from pinpoint papules to plaques covering broad swaths of body
- bleeding points appear when the scale is removed, traumatizing the dilated capillaries below (the Auspitz sign)
- Symmetric eruption (typically)
*
Classic presentation of psoriatic arthritis
Psoriasis vulgaris
Most common form (~90% of patients). Red, scaly, symmetrically distributed plaques characteristically localized to the extensor aspects of the extremities, particularly the elbows and knees, along with scalp, lower lumbosacral, buttocks, genitals, umbilicus and gluteal cleft. Single small lesions may become confluent, forming plaques in which the borders resemble a land map – “geographic” appearance.
Inverse psoriasis
Psoriasis lesions may be localized in the major skin folds, such as the axillae, the genito-crural region, and the neck. Scaling is usually minimal or absent, and the lesions show a glossy sharply demarcated erythema
Pustular psoriasis
usually preceded by other forms of the disease. Attacks are characterized by fever that lasts several days and a sudden generalized eruption of sterile pustules 2–3 mm in diameter. The pustules are disseminated over the trunk and extremities, including the nail beds, palms, and soles.
Erythrodermic psoriasis
Psoriatic erythroderma represents the generalized form of the disease that affects all body sites. Although all the symptoms of psoriasis are present, erythema is the most prominent feature, and scaling is different compared with chronic stationary psoriasis. Instead of thick, adherent, white scale there is superficial scaling. Patients with erythrodermic psoriasis lose excessive heat because of generalized vasodilatation, and this may cause hypothermia as well as electrolyte disturbances and rarely high-output cardiac failure.
Guttate psoriasis
characterized by eruption of small (0.5–1.5 cm in diameter) papules over the upper trunk and proximal extremities. Typically manifests at an early age, frequently in young adults.
Treatment of psoriasis
- Most cases treated topically
- Ointment formulations, topical glucocorticoids, improvement in 2-4 weeks followed by lower-dose maintenance treatment
- Vitamin D3 analogs like calcipotriene or anti-inflammatories like topical calcineurin inhibitors also effective
- Phototherapy using UVA and UVB light is also effective (mechanism seems to be apoptosis of TRM following a bout of Th2 inflammation in response to light)
- For severe cases, systemic corticosteroids, cyclosporine, retinoids, and anti-TNF/IL-17A/IL-22/IL-23 also useful
___ is a potentially life-threatening form of psoriasis, and any other form of psoriasis may progress to it.
Erythroderma is a potentially life-threatening form of psoriasis, and any other form of psoriasis may progress to it.
Psoriatic pitting of the nail
Yellow/brown psoriatic discoloration of nail
The onset of psoriasis in children often occurs as ___.
The onset of psoriasis in children often occurs as guttate psoriasis.
Guttate psoriasis
___ may follow a streptococcal infection of the upper resipiratory tract.
Guttate psoriasis may follow a streptococcal infection of the upper resipiratory tract.
Antigenic similarities between streptococcal proteins and keratinocyte antigens might explain the trigger
Psoriatic skin diagram (highlighting important characteristics)
Why is there so much keratinocyte proliferation in psoriasis?
IL-17 and IL-22 are keratinocyte growth factors!
Type I psoriasis
Earlier onset, more severe
Type II psoriasis
Later onset, milder form
Psoriatic endothelial dysfunction
Chronic systemic inflammation induced by psoriasis leads to insulin resistance in endothelial cells, which results in a reduction of NOS activity and thus vasoconstriction. Adhesion molecules are also chronically upregulated. Both of these provide an environment which favors the development of atherosclerosis.
Main type of T cell implicated in allergic contact dermatitis
T helper 1
So. . . yeah. . . Not so allergic after all
A common trigger for contact dermatitis in fragrances and soaps
Balsam of Peru
Koebner phenomenon
The traumatic induction of psoriasis on nonlesional skin; it occurs more frequently during flares of disease. The Koebner phenomenon is not specific for psoriasis but can be helpful in making the diagnosis when present.
