Dermatitis and eczema Notes

NOTES NOTES DERMATITIS & ECZEMA GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Inflammatory skin disorders ▪ Immune-mediated skin damage SIGNS & SYMPTOMS ▪ Rashes ▫ Pruritus (itching), burning, pain OTHER DIAGNOSTICS ▪ Rash ▫ Appearance, distribution TREATMENT MEDICATIONS ▪ Corticosteroids ▪ Immunosuppressants DIAGNOSIS LAB RESULTS ▪ Skin biopsy, blood tests ATOPIC DERMATITIS (ECZEMA) osms.it/atopic-dermatitis ▪ Allergic, inflammatory skin condition ▪ Common for children; may affect adults ▪ Associated with elevated serum IgE levels ▫ Atopy: predisposition to IgE antibody release after trigger exposure Type 4 hypersensitivity ▪ Primary immune dysfunction ▫ T cell subset imbalance → Th2 predominance → increased inflammatory cytokine production (IL-4, 5, 13) → increased release of IgE from plasma B-cells, recruitment of mast cells, eosinophils TYPES RISK FACTORS PATHOLOGY & CAUSES Type 1 hypersensitivity ▪ Epidermal barrier dysfunction ▫ Skin barrier defects (e.g. filaggrin mutation) → antigen entry → inflammatory cytokines 10 OSMOSIS.ORG ▪ Family history of atopy (eczema, asthma, allergic rhinitis) ▪ Environmental allergen sensitivities ▪ Loss of function mutation in filaggrin gene (skin barrier function)

Chapter 2 Dermatitis & Eczema ▪ Higher incidence in urban populations, high-income countries ▪ Low levels of early life exposure to endotoxin (immunogenic component of gram-negative bacteria) COMPLICATIONS ▪ Skin infections ▫ Staphylococcus aureus common commensal organism → impetigo ▪ Eczema herpeticum ▫ Rapid spread of herpes simplex virus on affected skin ▪ Social stigma, anxiety SIGNS & SYMPTOMS ▪ Acute ▫ Pruritic erythematous papules, vesicles with exudate, crusting ▪ Chronic ▫ Dry, excoriated erythematous papules with scaling; lichenification (hyperplasia) ▪ Dry skin ▪ Pruritus → chronic scratching → skin thickening, increased infection risk ▪ Cutaneous hyperreactivity to environmental antigens/stimuli (e.g. stress) ▪ 0–2 years old ▫ Erythematous, pruritic, scaly, crusted lesions +/- vesicles, serous exudate ▫ Extensor surfaces, cheeks, scalp ▪ 2–16 years old ▫ Lichenified plaques (thickened epidermis) ▫ Flexural distribution (e.g. antecubital, popliteal fossae); volar aspect of wrists, ankles, neck ▪ Adults ▫ Localized lichenified plaques ▫ Flexural surface involvement ▫ Uncommonly involves face/neck/hands DIAGNOSIS LAB RESULTS ▪ Elevated level of Serum IgE OTHER DIAGNOSTICS ▪ Morphology, distribution of lesions United Kingdom working group atopic dermatitis criteria ▪ Mandatory ▫ Evidence of pruritic skin with rubbing/ scratching ▪ ≥ three following criteria ▫ Skin crease involvement (antecubital fossa, popliteal fossae, neck, around eyes, ankles) ▫ History/first degree relative with asthma/hay fever ▫ Dry skin in past year ▫ < two years old before symptoms arose (not applicable to children < four years old) ▫ Visible dermatitis of flexural surfaces (< four years old → examine cheeks, forehead, outer aspects of extremities) Figure 2.1 Atopic dermatitis affecting the flexural surfaces of the forearms. TREATMENT MEDICATIONS ▪ Control pruritus ▫ Antihistamines ▫ Topical calcineurin inhibitors (tacrolimus ointment, pimecrolimus cream) ▫ Antibiotics to treat associated skin infections ▪ Immune suppression ▫ Topical → systemic corticosteroids OSMOSIS.ORG 11

▫ Topical calcineurin inhibitors ▫ Oral cyclosporine ▫ Dupilumab (IL-4 receptor antagonist) OTHER INTERVENTIONS ▪ Reduce exposure to environmental allergens ▪ Avoid triggers ▫ Heat, low humidity ▪ Manage stress/anxiety ▪ Maintain skin hydration ▫ Thick, unscented creams with low water content/ointments without water ▫ Apply after bathing/hand washing ▫ Avoid lotions with high water/low oil content (evaporation dries out skin, triggers outbreak) ▪ Control pruritus ▫ Prevent scratching; keep fingernails short (esp. young children) CONTACT DERMATITIS osms.it/contact-dermatitis PATHOLOGY & CAUSES ▪ Inflammation of skin after contact exposure to allergens/irritants ▪ Localized ▪ Exposure to foreign substance triggers immune response ▪ Most common form: irritant contact dermatitis CAUSES ▪ Exposure to irritant (irritation may be mechanical/chemical/physical) ▫ Acute: strong irritant ▫ Chronic: recurring exposure to weak irritant ▪ Detergents, surfactants, extreme pH, organic solvents, water ▫ Altered epidermal barrier function: Fat emulsion → defatting of dermal lipids → cellular damage to epithelium → DNA damage, transepidermal water loss → cytotoxic cell damage → cytokine release from keratinocytes → activation of innate immunity ▪ Plants with spines/irritant hairs ▪ Low humidity ▫ Skin loses moisture more easily 12 OSMOSIS.ORG Allergic contact dermatitis ▪ Anacardiaceae family plants ▫ Poison ivy, poison oak, poison sumac ▪ Nickel, fragrances, dyes ▫ Induction phase: immune system primed for allergic response to antigen ▫ Elicitation phase: contact allergens are typically haptens → small, can cross stratum corneum of skin to associate with epidermal proteins → form complete reactive antigen → dendritic cells recognise antigen → internalise antigen, transport to lymph nodes → present to T lymphocytes → trigger immune response → cell mediated immune response (Type IV delayed hypersensitivity) → memory cells remain within skin. Future exposure → triggers memory cells → immune response (cytokines, chemokines, TNF, lymphocytes, granulocytes migrate) RISK FACTORS ▪ Age ▫ Infants: highest risk ▫ > 65 years old: lowest risk ▪ Body site exposure ▫ Difference in thickness of stratum corneum, barrier function ▫ Face, dorsum of hands, finger webs are prone to irritation ▪ Atopy

Chapter 2 Dermatitis & Eczema ▫ Chronically impaired barrier function ▪ Occupational exposure ▫ Continuous moisture exposure, repeated cycles of wet-to-dry from frequent handwashing ▪ Allergic contact dermatitis ▫ Occupation (health professionals, chemical industry, beauticians, hairdressers, machinists, construction) ▫ Increases with age ▫ History of atopic dermatitis SIGNS & SYMPTOMS ▪ Erythematous rash (can develop ≤ 72hrs after exposure) ▪ Vesicles/bullae/wheals occur at exposure site ▪ Glaze/parched/scaled presentation ▪ Scaling, hyperkeratosis, fissuring ▪ Itching (favors allergic etiology); burning (favors irritant) TREATMENT MEDICATIONS ▪ Pruritus ▫ Calamine lotion ▪ Mild topical corticosteroid (hydrocortisone) ▪ Oral antihistamine ▪ Allergic contact dermatitis ▫ High potency topical corticosteroids ▫ Oral corticosteroids ▫ Topical calcineurin inhibitors (tacrolimus/ pimecrolimus) ▫ Systemic immunosuppression (azathioprine, mycophenolate mofetil, cyclosporine) OTHER INTERVENTIONS ▪ Remove/avoid trigger ▪ Treat blistering ▫ Cold compress ▪ Avoid scratching ▪ Retain moisture, protect skin ▫ Barrier cream (e.g. zinc oxide) ▪ Irritant contact dermatitis ▫ Mild acidic solutions (e.g. acetic acid) may neutralize alkali irritants/vice versa ▫ Emollients (e.g. Aquaphor) ▫ Gloves ▪ Allergic contact dermatitis ▫ Phototherapy (narrow band UVB radiation) Figure 2.2 Contact dermatitis secondary to poison ivy exposure. DIAGNOSIS OTHER DIAGNOSTICS ▪ History of possible exposure to irritant/ allergen ▪ Patch allergen testing OSMOSIS.ORG 13

SEBORRHOEIC DERMATITIS osms.it/seborrhoeic-dermatitis PATHOLOGY & CAUSES ▪ Sebaceous gland-centered skin inflammation ▪ Response to fungal antigens/irritants ▪ Chronic/relapsing ▪ Typically mild form of dermatitis CAUSES ▪ Occurs in sites with greater density of sebaceous glands ▪ Not a disease of sebaceous glands, nor increased sebum production ▪ Suspected connection to lipid-dependent fungal genus Malassezia ▫ Immune response to fungus ▫ Local irritants produced by fungus ▪ Children ▫ Nutritional deficiencies of biotin, pyridoxine (vitamin B6), riboflavin (vitamin B2) Distribution ▪ Areas containing significant number of sebaceous glands ▫ External ear, center of face, upper trunk, areas where skin rubs together ▪ Scalp ▫ Infants: aka cradle cap; self-resolving ▫ Adults: aka dandruff (pityriasis sicca); mildest form ▫ Fine, white scaliness without erythema +/- pruritus ▫ Severe cases: inflammation; patchy orange plaques with yellow, oily scales (pityriasis steatoides); may progress to oozing/crusting fissures affecting outer canal, concha of ear (vulnerable to superinfection) ▪ Face ▫ Forehead, eyebrows, glabella, nasolabial folds; may affect cheeks/malar area in butterfly distribution ▫ Frequently affects areas of facial hair distribution RISK FACTORS ▪ Age (biphasic incidence: 2–12 months of age to adolescence; adulthood: peaks 30s–40s) ▪ Hyperandrogenism ▪ Biological males > biological females ▪ HIV ▪ Parkinson’s ▪ Stress ▪ Cold, dry weather ▪ Sleep deprivation ▪ Poor general health SIGNS & SYMPTOMS ▪ Scaling erythematous plaques ▪ Scales yellow, oily in appearance Figure 2.3 Seborrhoeic dermatitis affecting both nasal folds. 14 OSMOSIS.ORG

Chapter 2 Dermatitis & Eczema ▪ Periocular ▫ Blepharitis, free margin redness ▫ Yellow crusting between lashes ▫ Can occur in isolation/part of larger distribution ▪ Trunk (five distinct patterns of distribution) ▫ Moist, skin-contact regions: axillae, inframammary folds, umbilicus, genitocrural ▫ Petaloid pattern: fine, scaling plaques over sternum/interscapular ▫ Annular/arcuate: round, scaly plaques, may have hypopigmented central clearing ▫ Pityriasiform pattern: mimics pityriasis rosea, 5–15mm oval, scaly lesions along lines of skin tension ▫ Psoriasiform pattern: large, rounded erythematous plaques with thick scales DIAGNOSIS OTHER DIAGNOSTICS ▪ History, appearance, distribution TREATMENT MEDICATIONS ▪ ▪ ▪ ▪ ▪ ▪ Topical antifungals Antifungal shampoo Topical corticosteroids Topical calcineurin inhibitors Oral antifungals Antiandrogens ▫ Reserved for individuals for whom feminization/male infertility is unproblematic ▫ Sexually-active, uterus-bearing people: combine with contraception to avoid risk to fetus OTHER INTERVENTIONS ▪ Cradle cap ▫ Apply emollient (petroleum jelly, vegetable oil, baby oil) to scalp overnight to loosen scales → remove scales with soft toothbrush ▫ Frequent shampooing with mild, nonmedicated baby shampoo → remove scales with soft toothbrush ▫ Extensive/persistent cases → medical therapy ▪ Topical ▫ Coal tar shampoo/ointment OSMOSIS.ORG 15