Cutaneous Immunology Flashcards
Cutaneous lymphocyte antigen
Expressed by activated T cells, allowing them to enter blood stream and migrate to inflamed skin to generate further inflammation
TH1 Cells (cytokines, cell activation, hypersensitivity, associated diseases)
Release IFNg and TNF to activate cellular immunity, such as macrophages, neutrophils, and cytotoxic T cells, which kill infected cells and tumors.
Responsible for delayed / type IV hypersensitivity, which is involved in contact dermatitis, psoriasis, and drug exanthem.
IFNg blocks TH2 cells.
TH2 Cells (cytokines, cell activation, purpose, associated diseases)
Release IL-4, 5, and 10 to activate humoral immunity, which includes eosinophils, plasma cells, and IgE to attack larger pathogens that are too large to be inside cells, such as parasites. Also neutralize toxins.
Associated w/ atopic dermatitis, urticaria, and asthma.
IL-10 blocks TH1 cells
Which diseases are associated w/ TH17 cells?
Associated w/ autoimmune diseases, such as psoriasis, ulcerative colitis, and Crohn’s disease
Allergic Contact Dermatitis (hypersensitivity type, sxs, diagosis, sensitization)
TH1 / delayed / type IV hypersenstivity.
Itchy erythematous papules and vesicles on area exposed to allergen
Diagnosed w/ patch testing
Sensitization takes 7-14 days (first exposure). Re-exposure occurs more quickly as memory T cells migrate quickly to skin and releases cytokines.
Atopic Dermatitis / Eczema (cause, hypersensitivity, sxs, location [adults vs infants], associated diseases)
Fillagrin defect → barrier dysfunction → allergens → reinforcement of TH2 hypersensitivity → IL release → humoral response
Scaly, ill-defined, erythematous patches. May be lichenified. Itchy.
Adult location: Face, neck, and flexural areas
Infant location: Face, extensor arms / legs, and butt (from crawling / sitting)
Associated w/ atopic triad, keratosis pilaris, and pityriasis alba
Psoriasis (sxs, location, hypersensitivity, hallmark histology, types, tx)
Erythematous plaques w/ silvery, micaceous scale on extensors, scalp, sacrum, groin, and nails (oil spots).
Trauma to skin → TH1 → IFNg / TNF → keratinocyte proliferation → hyperkeratosis. TH17 also stimulates proliferation.
Presence of neutrophils (recruited by TH1 cells) is hallmark histologic characteristic.
Guttate psoriasis – precipitated by strep infection.
Pustule psoriasis – pustules may be localized to palms / soles, or generalized.
Inverse psoriasis found in clefts, such as butt / groin.
Erythrodermic psoriasis covers entire body
Tx w/ topical steroid, or in severe cases, T cell / TNF receptor blockers.
Urticaria / Hives (sxs, cause, hypersensitivity, hallmark, pathogenesis, test, tx)
Itchy annular, edematous pink plaques (wheals). Dermatographism and angioedema.
Mediated by mast cells and histamine release (type 1 / immediate hypersenstivity)
Hallmark is evanescence – comes and goes w/in 24 hrs
Plasma cells secrete IgE, which is primed onto mast cell looking for allergens.
Antigen-IgE complex, scratching, and medications can all cause histamine release → vasodilation / fluid accumulation → urticaria within minutes.
Test w/ skin prick testing.
Tx w/ antihistamines.
Angioedema
Deep form of urticaria that commonly affects lips and face.
Exanthematous Drug Eruptions (cause, timeframe, hypersensitivity, sxs)
Due to TH1 hypersensitivity.
Occurs 4-14 days after taking medication and may last 1-2 weeks after drug is stopped. Delayed type IV hypersensitivity.
Itchy, but not harmful.
Morbilliform eruption – measles-like. Red macules / papules on central body and extremities. Similar to viral rash b/c drug gets into cells.
DRESS (name, sxs, hallmark, timeframe, associated diseases)
Drug eruption w/ eosinophilia and systemic sxs Exanthematous eruption w/ fever, lymphadenopathy, and facial edema (hallmark). Sheets of desquamation may occur.
Onset is 15-40 days.
Mortality may occur due to fulminant hepatitis.
Urticarial drug eruptions (cause, hypersensitivity, timeframe, sxs)
Mediated by IgE activation of mast cells. Occurs w/in minutes to hours (type 1).
Can also lead to angioedema and anaphylaxis
SJS / TEN (name, cause, sxs, Nikolsky, timeframe)
Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis
Very serious drug eruption → cascade of epidermal apoptosis → widespread necrosis → sheets of sloughed skin.
Severe pain, dusky red macules, bullae w/ + Nikolsky, and mucosal erosions on head, trunk, and extremities. Hemmorhagic crusting of lips.
PAIN and fever.
Occurs 1-3 weeks after taking drug.
