Cutaneous Immunology

Question 1

cutaneous lymphocyte antigen (CLA)

Answer 1

expressed by langerhans and dermal dendritic cells

cell-surface markers that allows them to enter bl. stream and migrate to inflamed skin –> generate further inflam and coordinate immune response

Question 2

TH1 cytokines

Answer 2

INF-gamma, TNF (IL-2)

*virus, tumor, intracell pathoge

Question 3

TH2 cytokines

Answer 3

IL-4, 5, 10

*parasites, extracell microbes

Question 4

TH17 cells

Answer 4

role in autoimmune disease (Crohns, ulcerative colitis, psoriasis)

Question 5

allergic contact dermatitis (ACD)

Answer 5

aka: contact hypersensitivity
local inflam to perceived threat of allergen

clin appear: itchy red papules and vesicles 24-48 hrs after exposure (if reexp), worsen for 4-7 days (bullae, scale, lichenification w/ greater severity)

path testing to determine offending allergen

patho: inflam thru type IV/delayed hypersensitivity
- most contact allergens are happiness (small so penetrate epidermis and cause rxn when bound to native proteins)
- initial activation, prolif, anf differentiation takes 7-14 days first exposure often doesn’t produce response
- Th1 dominates

Question 6

atopic dermatitis (eczema)

Answer 6

looks similar to ACD, but is Th2 dominated (immune system imbalance not hypersens to single substance)

atopic triad (eczema, asthma, allergic rhinitis)

clin appear: generalized itchy skin, ill defined erythematous papillose and plaques w/ scale and crust

• infants: face, scalp, extensor surfaces
• adults: flexor areas and face

patho:
- genetics: mut in filaggrin
- allergens: inoculation w/ dust mite –> Th2
* *risk for viral infections b/c dcr. Th1 (eczema herpeticum)
- staphyloccocus aureus superinfection

Question 7

psoriasis

Answer 7

keratinocytes prolif at inc. rate and epidermis thickens (b/c cytokine signals)

clin. appear: erythematous, well demarcated plaques w/ thick, silvery white scale
- extensor areas*, trunk, extrem, genitals most (Koebner phenomenon: scratching leads to outbreaks in these areas)
- oil spots and thickening on nails (–> destructive/psoriatic arthritis)

“Guttate psoriasis”: small round papillose and plaques, often from strep

patho: Th1 dominates, presence of neutrophils in epidermis
treatment: chemotherapeutics that target T cells or block TNF receptor, block Th17

Question 8

urticaria (hives)

Answer 8

clin pre: itchy, annular, edematous, pink papules or plaques wheals, evanescence (each lesion develops and resolves in 24 hrs)

• dermatographism: linear wheals where scratching
• angioedema: urticaria in deep dermis, painful swelling of face and lips

patho: mast cell w/ degran (IgE, drugs, physical stim) and histamine release (end result of type I/immediate hypersensitivity)

Question 9

exanthematous (morbilliform) drug eruptions

Answer 9

drugs and metabolites are distributed on skin and cause type IV/delayed hypersensitivity (Th1) –> 4-14 days

don’t progress to more severe rxns

begin as erythematous merciless and papillose on trunk and upper extrem. and progressively spread outwards

DRESS (drug eruption w/ eosinophilia and systemic symptoms): exanthematous eruption w/ fever, lymphadenopathy and facial edema
-onset is 15-40 days

Question 10

urticarial drug eruptions

Answer 10

due to systemic meds
occur w/in minutes and patient has IgE against drug (immediate/type I hypersens)
angioedema can be life threatening

Question 11

Stevens Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN)

Answer 11

immune system activates cascade of apoptosis –> widespread epidermal necrosis

• erythematous and dusky merciless –> patches on head, trunk, extremities
• mucosal ulcerations, bullae, sloughing in sheets
• fever
• painful

onset is 7-21 days