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Medicine Notes Dermatology Notes

Dermatology Notes

Updated Dermatology Notes

Dermatology Notes

Dermatology

Approximately 27 pages

Undergraduate Medicine Degree. Year 4 Dermatology module
Includes:
- Melanocytic and non-melanocytic lesions
- Leg ulceration
- Eczema
- Skin manifestations of systemic disease
- Bacterial + viral infections
- Psoriasis
- Acne
- Fungi and infestations...

The following is a more accessible plain text extract of the PDF sample above, taken from our Dermatology Notes. Due to the challenges of extracting text from PDFs, it will have odd formatting:

Contents

Melanocytic Lesions 2

Melanocytic Naevi: 2

Malignant Melanoma: 2

Non-melanoma Cancers and Benign Tumours 2

Benign Tumours of Epidermis + Appendages 2

Premalignant Tumours of Epidermis + Appendages 4

Malignant Epidermal Tumours 5

Benign Dermal Tumours 9

Leg Ulceration 10

Eczema 11

Atopic Eczema 12

Seborrhoeic Eczema 13

Asteototic Eczema 13

Gravitational Eczema 13

Discoid (Nummular) Eczema 14

Contact Dermatitis – irritant 14

Contact Dermatitis – allergic 14

Hand Dermatitis 14

The Skin and Systemic Disease 14

Drug Eruptions 15

Examples 16

Bacterial + Viral Infections 17

Commensal and Pathogenic Bacteria 18

Pathogenic Viruses 19

Psoriasis 21

Clinical Features 21

Treatment 22

Acne 23

Fungi and Infestations 25

Fungi 25

Infestations 27

Melanocytic Lesions

Melanocytic Naevi:

  • Melanocytes which fail to mature or migrate in utero

  • Congenital: 1% of children have small naevi (rare giant ‘bathing trunk’ naevi – high risk of malignancy; Mongolian blue spot – due to melanocytes in dermis, benign)

  • Acquired: develops after birth (usually <25 years old)

    • Junctional – macular

    • Compound – ‘warty’

    • Intradermal – smooth + dome shaped

    • Halo naevus – undergoing regression, benign

    • Blue naevus – melanocytes in dermis, usually benign, often extremities

Sinister features:

  • 50% of melanomas arise from naevi

  • Changes in size

  • Irregular shape

  • Irregular colour

  • >1cm diameter

  • Itch

  • Bleeding/ulceration

Malignant Melanoma:

  • Types:

    • Superficial spreading (common, usually legs in women + trunk in men)

    • Nodular (poor prognosis, may be amelanotic)

    • Lentigo maligna melanoma (usually on face in elderly, arise within lentigo maligna)

    • Acral (palms or soles, can occur in Asian or Afro-Caribbean)

Treatment:

  • Excision: optimum excision margin unknown, generally 1cm for every 1mm depth invasion

  • Chemotherapy or immunotherapy of limited use

Prognosis:

  • Depends on depth of invasion, or Breslow thickness (depth in mm from granular cell layer)

  • 5YSR: depth<1.5mm (90%), 1.5-3mm (60%), >3mm (40%)

Non-melanoma Cancers and Benign Tumours

Benign Tumours of Epidermis + Appendages

Squamous cell papilloma

  • Common tumour, arises from keratinocytes

  • May resemble viral wart clinically

  • Excision, or curettage with cautery to base is treatment of choice + histology should be checked

Seborrhoeic keratosis (basal cell papilloma, seborrhoeic wart)

  • Common benign epidermal tumour, unrelated to sebaceous glands

  • Cause: usually unexplained. Multiple lesions may be inherited (autosomal dominant), occasionally follows inflammatory dermatosis

  • Presentation: usually arise after age 50 (but flat inconspicuous lesions often visible earlier). Often multiple but may be single. Lesions more common face + trunk. Distinctive ‘stuck-on’ appearance; may be flat, raised or pedunculated; colour varies from yellow to dark brown and surface may have greasy scaling + scattered keratin plugs (‘currant bun’ appearance). Lesions may multiply with age but remain benign

  • DD: pigmented naevus, malignant melanoma, basal cell carcinoma (BCC), Afro-Caribbeans may have dermatosis papulosa nigra

  • Ix: biopsy needed only in rare dubious cases. Histology is diagnostic – lesions lies above general level of surrounding epidermis + consists of proliferating basal cells + horn cysts

  • Treatment: can safely be left alone. Ugly/easily traumatised ones can be removed with curette under local (also provides histology), or by cryotherapy

Skin tags (acrochordon)

  • Common benign outgrowths of skin. Affect mainly middle-aged + elderly

  • Cause: unknown. Trait is sometimes familial. Most common in obese women. Rare associations = tuberous sclerosis, acanthosis nigricans, acromegaly, diabetes

  • Presentation: occur around neck + within flexures. Look unsightly + may catch on clothing/jewellery. Soft, skin-coloured or pigmented pedunculated papules

  • DD: rarely confused with small melanocytic naevi

  • Treatment: small lesions snipped off with fine scissors, frozen with liquid nitrogen or destroyed with hyfrecator without local anaesthetic. No way of preventing new ones.

Linear epidermal naevus

  • These lesions are an example of cutaneous mosaicism and so tend to follow Blashko’s lines

Epidermoid and Pilar cysts

  • Common. Occur on scalp, face, behind ears, trunk

  • Often have a central punctum which secretes foul-smelling material when ruptured

  • Histologically, the lining of the cyst resembles normal epidermis (epidermoid) or outer root sheath of the hair follicle (pilar)

  • Occasionally, an adjacent foreign body reaction is noted

  • Treatment: excision, or excision followed by expression of contents + removal of cyst wall

Milia

  • Small subepidermal keratin cysts

  • Common on the face in all age groups

  • Appear as white millet seed-like papules of 0.5-2mm diameter. Occasionally seen in sight of previous subepidermal blister (e.g. in epidermolysis bullosa or porphyria cutanea tarda)

  • Contents of milia can be picked out with sterile needle without local anaesthesia

Chondrodermatitis nodularis helicis (painful nodule of the ear, ear corn)

  • Strictly, not a neoplasm, but a chronic inflammation

  • Painful nodule develops on helix (or antehelix) of ear, most often in men

  • Looks like small corn, tender and prevents sleep

  • Histologically, thickened epidermis overlies inflamed cartilage

  • Treatment: wedge-resection under anaesthetic successful if cryotherapy or Intralesional triamcinolone (steroid) injection fails

Premalignant Tumours of Epidermis + Appendages

Keratoacanthoma

  • Some argue that this rapidly growing tumour should be classified as benign, but some do transform into squamous cell carcinoma

  • Cause: photosensitising chemicals (e.g. tar, mineral oils) act as cocarcinogens with UVR. They may also follow therapeutic immunosuppression

  • Clinical features: mainly occur on exposed skin in fair individuals. 2/3 on face, most of the rest on the arms. Lesion starts as a pink papule that rapidly enlarges (may reach 1cm in 1-2months). After 5-6weeks, centre of the nodule forms either a keratinous plug or a crater. If left, lesion...

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