Eczemas

Question 1

Eczematous dermatitis

Answer 1

• Inflammation of the skin
• Can be due to too much hygiene, too little infection, allergies, genetics (multi-factorial etiology)
• Onset usually around 6 mod
• Broad range of inflammatory conditions

Question 2

Atopic dermatitis (AD)

Answer 2

• The itch that scratches
• Along w/ asthma and allergic rhinitis forms atopic triad
• Genes controlling AD related to inflammation and immune response
• Characterized by: pruritus, dry/scaly skin, crusted rashes, small weeping papules, thickening of skin (lichenification), redness and swelling

Question 3

Stages of AD

Answer 3

• More acute in infancy, usually in face, scalp, extensor surfaces
• In adulthood moves to flexor folds
• Infantile (0-2 yrs), childhood (2-12 yrs), adulthood (puberty onward) stages
• In adults chronic hand AD is most common

Question 4

Associated manifestations of AD

Answer 4

• Ichthyosis vulgarism (dry rectangular scales)
• X-linked ichthyosis (male only)
• Deanie-morgan fold (lower eyelid dermatitis)
• Hertoghe sign (loss of lateral part of eyebrow)
• hyper linearity of palms
• Increased risk of cataracts

Question 5

Immunology of AD

Answer 5

• Increased IgE production (type I hypersensitivity rxn), decreased CD8 but increased CD4 T cell number
• Leads to elevated TH2 cell number and release of IL4 and IL10
• Increases susceptibility to infections due to decrease in antimicrobial peptides (defensins and cathelicidins)
• Mutation in filaggrin predisoposes to AD and asthma. Leads to more permeable skin

Question 6

Dx criteria for AD

Answer 6

-Pruritus, lichenification, chronic or relapsing course, personal or family history of atopic triad

Question 7

Rx for AD

Answer 7

• Avoid triggers (cold, stress, irritants, allergens, food, infection)
• Control dry skin (emollients/moisturizers, ceramics to restore stratum corneum)
• Rx infection/inflammation (antibios, bleach baths, antivirals, topical steroids)
• For itching use antihistamine as a sedative

Question 8

Associated diseases of AD

Answer 8

• Eczema herpeticum (HSV superinfection)
• Eczema vaccinatum (superinfection of vaccinia virus due to smallpox vaccine)
• Staph superinfection
• Molluscum contagiosum (pox virus superinfection)
• Keratosis pilaris (monomorphic keratotic papules)
• Pityriasis alba (post inflammatory hypopigmentation)
• Seborrheic dermatitis

Question 9

Irritant contact dermatitis

Answer 9

• More common form of contact dermatitis (CD)
• Non-immunologic (not based on memory, occurs at first exposure)
• Caused by direct toxic effects on skin
• Normal epidermis is disrupted and leads to inflammation

Question 10

Allergic contact dermatitis

Answer 10

• Less common, mediated by delayed type IV hypersensitivity reaction (requires memory)
• Langerhans APCs capture Ag and present to naive T cells which become memory T cells
• On second exposure there is a large TH1 response resulting in dermatitis
• Dx is patch testing (TRUE)

Question 11

Allergens vs irritants

Answer 11

• Some can be both (plants and latex/rubber)
• Allergens: metals (nickel), fragrances, plastics, topical meds, hair products, clothing dyes, leather
• Irritants: water, skin cleanser, cleaning agents, chemicals

Question 12

Latex/rubber allergy

Answer 12

• Causes type I, type IV, and irritant hypersensitivity rxn
• High risk factors: AD, multiple surgeries in 1st year of life (spina bifida)
• Cross rxns: avocado, banana, kiwi, chestnut (BACK)

Question 13

Plant allergic contact dermatitis

Answer 13

• Can also be phytophotodermatitis (sunlight cross reacts w/ plant juices)
• poison oak/ivy contains urushiol which causes the most common allergic contact dermatitis
• Rx is to wash off
• Cross reacts w/ cashew, mango skin, gingko, lacquer tree