Teaching Clinic: Common Dermatoses Flashcards
Clinical assessment of Skin
- Morphology + Distribution
- Colour
- Shape
- Border
- Surface
- Pattern: linear, annular, grouped, reticular - Inspection + Palpate
- Type of lesion
- Primary lesions: macule, patch, papule, nodule, plaque, pustule, vesicle, bulla, blister, wheal, telangiectasia etc.
- Secondary lesions: crust, excoriation, lichenification, scar, scaling, exfoliation, fissure, erosion, ulcer, atrophy etc.
Urticaria vs Angioedema
Both involve the same edematous process, but at different levels of the cutaneous vascular plexus
Urticaria:
- Composed of wheals (transient edematous papules and plaques), usually pruritic, due to edema of papillary body)
- Acute
- Acute onset, lasts **<6 weeks
- Often **IgE-dependent with atopy (e.g. triggered by parasites, drugs, alimentary agents)
- Can be complement-mediated (e.g. serum-sickness like reaction)
- Common: Infection-related - Chronic
- Lasts ***>6 weeks
- Rarely IgE-dependent
- Mostly “idiopathic”
DDx:
1. **Urticarial vasculitis
2. **Drug eruption
3. **Viral exanthem
4. Bites / Papular urticaria
5. **Bullous pemphigoid
Treatment:
1. Discontinue suspected triggers
2. Anti-histamines: Sedative / Non-sedative
3. Immunosuppressants
- Corticosteroid (Topical steroids: not generally effective)
- Cyclosporine, Azathioprine
4. Biologic: Anti-IgE (Omalizumab)
Angioedema:
- Larger edematous area that involves dermis & subcutaneous tissue
- Deep, ill-defined
Atopic eczema
- Chronic relapsing pruritic exanthematous dermatosis
- Characterised primarily by an **allergic diathesis, **erythema, oozing, crusting, excoriations, lichenification and dehydration of involved skin
Established criteria for diagnosis:
1. Hanifin + Rajka’s criteria (3 major + 3 minor criteria)
2. 1994 UK Working Party’s diagnostic criteria (pruritus and 3 of flexural involvement, asthma / hayfever, generalized dry skin, onset under 2 year old)
Distribution: **Age-dependent
- Infant: **extensor surfaces of limbs, face, neck, scalp, trunk
- Child: **flexures, trunk
- Adolescent: neck, face, **extensor surfaces of upper and lower limbs, breasts, hands
Morphology:
- Ill-defined border, symmetrical
- Acute / Subacute / Chronic
Complications:
- Secondary infections e.g. Impetigo, Cellulitis
DDx:
- **Seborrhoeic dermatitis
- **Contact dermatitis
- ***Psoriasis
- Scabies
Contact dermatitis
- Contact Irritant Dermatitis
- inflammatory reaction in the skin resulting from exposure to a substance that causes an eruption in most people who come in contact with it - Contact Allergic Dermatitis
- **acquired sensitivity to various substances that produce inflammatory reactions in those, and only those, who have previously been **sensitised to the allergen
Patch test:
- Intact, uninflamed skin
- Upper back
- Non irritating concentration of suspected substances / allergens
- Patches removed after 48 hours
- Assess for reaction at 48 hours and at 96 hours
- Erythematous papules, vesicles, oedema
- “Excited skin syndrome”: state of hyper-irritability. Negative tests may appear as weakly positive
Psoriasis
Classification:
1. **Psoriasis vulgaris
- Chronic plaque psoriasis
- Guttate psoriasis
- Inverse psoriasis
- Palmoplantar psoriasis
2. **Erythrodermic psoriasis
3. ***Pustular psoriasis
- Von Zumbusch’s disease
- Palmoplantar pustulosis
- Acrodermatitis continua
Clinical features:
1. **Chronic large plaque
2. **Guttate
3. **Pustular
4. **Erythoderma
5. **Nail
- Pitting
- Onycholysis
- Subungual hyperkeratosis
- Oil-drop sign
- Nail dystrophy
6. **Scalp / Joints
7. **Auspitz sign (small bleeding points after successive layers of scale have been removed from the surface of psoriatic papules or plaques)
8. **Koebner phenomenon (appearance of new skin lesions on previously unaffected skin secondary to trauma)
Management principles depend on:
1. Age
2. Type of psoriasis
3. Site, extent of involvement
4. Previous treatments
5. Associated medical disorders
6. Lifestyle of patients
Treatment:
1. Topical
- Emollient
- **Corticosteroid
- **Vitamin D analogue
- ***Coal tar
- Tazarotene
- ***Phototherapy
- NBUVB, PUVA - Systemic treatment
- Methotrexate
- ***Retinoids
- Cyclosporine - Biologics
- Anti-TNF (Infliximab, Etanacept, Adalimumab)
- Anti-IL12/23 (Utekinumab)
- Anti-IL17 (Secukinumab)
- JAK inhibitor (Tofacitinib)
- PDE-4 inhibitor (Apremilast)
Impetigo
Causative organisms:
- **Staphylococcus / **Streptococcus
Clinical features:
- **Vesicles / **Pustules that arise on **erythematous base with **crusting formation
- In skin damaged by previous minor trauma such as scratching / insect bite
DDx:
- Discoid eczema
- Herpes simplex
- Varicella
Treatment:
1. Topical / Systemic antibiotics
- ***Cloxacillin, Cefuroxime, Erythromycin
Complication:
- ***Post-infective glomerulonephritis
Dermatophytic infection
- Tinea unguium / Onychomycosis (nail)
- Tinea pedis (feet)
- Tinea cruris (groin)
- Tinea corporis (trunk)
- Tinea manuum (hands)
- Tinea capitis (scalp)
Viral warts
Causative organism:
- ***Human Papilloma Virus (HPV)
- Transmitted by contact
- Genital wart: sexually transmitted
Clinical features:
- Warty lesions with blood vessels beneath surface
- Painful in sole
- Genital wart can be associated with ***neoplastic changes (e.g. SCC in-situ, SCC)
Treatment:
1. **Salicylic acid
2. **Cryotherapy + Cauterization
3. ***Topical 5% imiqimod
Herpes zoster
- Reactivation of latent VZV
- Usually elderly
Clinical features:
- **Dermatomal distribution
- **Painful erythematous eruption followed by **Vesicle + Pustules formation that clustered into a **herpetiform arrangement
- Affect ***eye If involve Trigeminal nerve
Complications in immune competent patients:
1. Peripheral nerve palsies
2. Encephalitis
3. Myelitis
4. Contralateral hemiparesis
Acne vulgaris
- Common in teenage (80%)
- M>F
- Positive Family history
- Often neglected: asymptomatic, not life-threatening
- Some patients / parents considered acne to be “normal” for puberty
Pathogenesis:
1. Seborrhoea
- **Excessive sebum production due to over-response to **androgens or excessive androgen secretion
2. **Comedogenesis
- Hypercornification of pilosebaceous ducts
3. Infection
- **Propionibacterium acnes (P. acnes)
4. Inflammation
- **Lipolysis of sebum of P. acnes
- Superantigen from P.acnes triggers **inflammation of comedones
- Inflammatory mediators from ductal corneocytes
Clinical features:
1. Comedones
- Open / Closed
- Non-inflamed
2. Papules, pustules
- Superficial inflamed lesions
3. Nodules, cysts
- Deep inflamed lesions
Treatment:
1. Topical therapy
- **Retinoids
- **Benzoyl peroxide
- **Azelaic acid
- **Antibiotics
2. Oral therapy
- Antibiotics
- OC pills
- **Isotretinoin (Roaccutane): Stop contraception **1 month after completion of isotretinoin
