Dermatology SC024: I Have An Itchy Rash (Eczema, Urticaria, Tinea Infection And Psoriasis) Flashcards
History taking in Acne
- Onset
- Duration
- Symptom (itch, pain)
- Provocative / Alleviating factors
- Location
- History of Atopy (asthma, allergic rhinitis)
- Family history of acne scarring (scarring can be genetically related)
- Psychosocial impact
Acne
- Common in teenage (80%)
- M>F
- Family history +ve (esp. for scarring)
- Often neglected: asymptomatic, not life threatening
- Some patients / parents consider acne to be normal for puberty
- Main problem with Acne: ***Scarring (e.g. Keloid)
Etiology:
1. Sex hormone
- ***Testosterone: a definite role
- ↑ Sebum production
- M>F
- Female: flare up occur with menstrual period (when estrogen ↓ —> testosterone ↑), irregular period more resistant to treatment
- Sebum production
- Hormone
- ?Genetic
- ?Food (carbohydrates —> insulin —> growth factor effect —> enhance keratinocyte proliferation)
- Together with dead cells block hair follicle —> comedome (blackhead) -
**Bacteria proliferation
- **Propionibacterium: P. acnes, P. avidum, P. granulosum (can be antibiotic-resistant —> antibiotic use limited to 3 months + Keratolytic agent / Retinol to prevent resistance)
- Blockage of hair follicle —> Serum attract bacteria —> Bacteria proliferation causing inflammation —> Inflammed hair follicle —> Red papule - Host response
- Defence mechanism against bacteria proliferation —> WBC infiltration —> Secretion of enzyme that lead to non-specific destruction of bacteria + dermal tissue —> Pustules, scarring, cyst formation
Pathogenesis:
- Sebum from sebaceous gland + Dead keratinocyte
—> Block hair follicles (Blackhead) to prevent sebum excretion
—> Sebum collection cause bacterial overgrowth
—> Inflammed hair follicle
—> WBC collection in follicle
—> Pustules
Clinical features:
- Comedome (blackhead)
- Papule (red)
- Pustule
- Scarring
- Cyst
Treatment for Acne
- Topical
- **Benzoyl peroxide
- **Antibiotic
- **Retinoid (e.g. Tretinoin)
- **Azelaic acid
- Sulphur
Normal use: Antibiotic cream —> step up to Benzyol peroxide / Azelaic acid —> Retinoid therapy 1 month later (can lead to acne flare when initiating ∴ need to use other agents first to control acne) (step up strength of Retinoid every 4-6 weeks then maintanence)
- Systemic
- Antibiotic
- Hormonal therapy
- ***Isotretinoin
Previous indication of systemic therapy:
- Moderate to severe acne
- Depressed
- Significant post-inflammatory hyperpigmentation
- Acne-excoriee
- Acne keloidalis
- Gram -ve folliculitis (resistant to Tetracycline —> need skin swab)
Recent trend:
- Start early treatment to prevent scarring
- Oral contraceptive (reduce effect of testosterone) + antibiotic for 3-4 months —> gradual step up to cream —> cream only for long term
- Ablative resurfacing (aka Laser) (gold standard)
- Fractional photothermolysis
Benzoyl peroxide
- Conc: 2.5-10%
MOA:
- ***Keratolytic agent —> unblock hair follicle
- Reduce comedomes
- Suppress skin surface free acid
- Reduce skin surface bacteria
- Use in combination with other topical therapy esp. Antibiotic to prevent antibiotic resistance
SE:
- Irritation
- Dryness
Azelaic acid
MOA:
- ***Keratolytic
- Reduce free fatty acid + bacteria load
(- Lightening effect: less post-inflammatory hyperpigmentation)
- As effective as Benzyol peroxide, Retinoid, Tetracycline
SE:
- Mild irritation
Antibiotics
Topical: Erythromycin, Tetracycline, Clindamycin
- use in combination with other topical therapy e.g. Benzyol peroxide / Retinoid
- MOA: ***Anti-microbial effects: reduce P. acnes
Systemic:
1. Tetracycline / related
2. Erythromycin / related
MOA:
- Anti-microbial
- ***Anti-inflammatory (take 3 weeks to work, 1 course ~3-4 months —> step up topical medications meanwhile)
SE:
- GI (take probiotic)
- Rarely for Tetracycline group: Phototoxic, Liver damage, SLE-like
- Relapse if discontinued
Retinoid
Topical:
- Tretinoin, Isotretinoin
Systemic:
- Isotretinoin
MOA:
- ***Vit A analogue —> regulate epithelial cell growth
- Reduce comedogenesis
- Reduce inflamed + non-inflammed lesions
(- Reduce sebum production)
SE:
- Irritation
- Dryness
CI:
- Avoid in pregnancy (Teratogenic): Stop contraception ***1 month after completion of isotretinoin
Examples:
1. Adapalene gel
- new generation of topical retinoid
- as effective as tretinoin 0.025% but less SE (scaling, irritation, erythema)
- gel / cream preparation
Isotretinoin
- Only effective mean to long term cure
- Significant SE
- Only dermatologist can use the treatment
MOA:
- ***Reduce sabaceous gland volume —> reduce sebum production
- Alter cutaneous immunological function
SE (significant):
- **Teratogenicity (cleft palates, neurological problems affecting 4-7% of baby) —> need to have contraceptive method: Stop contraception **1 month after completion of isotretinoin
- Chelitis
- Conjunctivitis
- Myositis
- Arthralgia
- Hair loss
- **Liver impairment —> check LFT (baseline + 4 weeks)
- **Raised TG —> check TG + lipid (baseline + 4 weeks)
- Raised benign ICP
- Headache
- ***Mood changes —> relative CI in previous depression
Hormonal therapy
- Oral contraceptive / Anti-androgen (Cyproterone)
- For female that have hormonal disturbance / contraceptive needs
- Takes 4-6 weeks to improve
SE:
- Relapse if discontinued
Ablative resurfacing (aka Laser)
Gold standard
Several problems:
- “Unforgiving” system
- Pain, oozing, prolonged erythema
- Risk of infection + scarring
- Can leave unnatural skin sheen
- Avoid certain skin surfaces —> scar
- Pigmentary problems
Example:
- Fractional photothermolysis
History of Eczema
- Itchiness
- Area: Flexural area of limb
- Family history of atopy (asthma, allergic rhinitis, eczema —> lungs, nose, skin are organs most exposed to external environment)
Atopic march: Difference in prevalences of allergic diseases
- ?Allergen load
- ?Tolerance
- ?Differ in immunological response
Approach to Dermatitis
- History
- Onset
- Duration
- Site
- Occupation
- Atopic tendency
- Family history - P/E
- Type
- Distribution
- Arrangement
- Secondary changes
- Nail, Scalp, Back of ear, Genitalia - Investigation
- Patch test (allergic test)
Classification of Dermatitis
- Endogenous
- Atopic dermatitis - Exogenous
- Primary irritant
- Allergic contact
ALL 3 can ***overlap
Patch test
Indications:
- Dermatitis for hands, feet, face, legs that persist despite avoiding irritant
- Chronic medicament use
- Atypical / Persistent discoid eczema
Screening series:
- Metals
- Rubber chemical
- Medicaments
- Cosmetics
- Balsams
- Others (e.g. Preservatives, Metal impurities)
NOT the same as Skin prick test:
Patch test:
- Detect allergic contact dermatitis (**Type 4 hypersensitivity reaction)
- Allergy to hair dye, shoes, active ingredients, preservative and fragrances in sunscreens, cosmetics and medicaments
- Allergic reactions usually appear **2 to 4 days after applying the allergen on the skin but it can take up to a week to react
Skin prick test:
- Test **Type 1 allergy causing hay fever, asthma and contact urticaria (hives)
- Involves needle pricking
- Results read **20 minutes after skin pricking
Atopic eczema (Atopic dermatitis / AD)
- Associated with asthma, allergic rhinitis (***Atopic march)
- Early onset <2
- Genetic predisposition (one parent: 30%, both: 80%)
- Due to immunological imbalance (in skin, tendency to mount reaction against harmless substance e.g. food, pollutants but diminished reaction against harmful substance e.g. bacteria)
- Common in HK: 5-28%
4 problems:
1. Weakened immunological system against pathogens
2. Reduced ability to preserve water —> Transepidermal water loss
3. Infection / Scratching make thing worse (scratching —> skin cell protein (e.g. keratin) can mimic allergens —> simply avoiding allergen does not help)
Clinical features:
- ***Itchy rash
- Ill-defined Erythema (vs Psoriasis: more defined), Papules, sometimes Maculo-papular eruptions —> scratching —> may cause Lichenification (secondary changes)
- Infants: Face + Extensor surface
- Children: Flexural surface
- Chronic + Relapsing in nature
- Dry skin
