dermatology_N.Shear.pdf

DERMATOLOGY

Dr. N. Shear

Blaise Clarkson and Elana Lavine, chapter editors

Harriette Van Spall, associate editor

Primary Morphological Lesions

Secondary Morphological Lesions

Other Morphological Lesions

USEFUL DIFFERENTIAL DIAGNOSES . . . . . . . 3

Differential Diagnosis by Morphology

Differential Diagnosis by Location

COMMON SKIN LESIONS . . . . . . . . . . . . . . . . . . 5

Hyperkeratotic

Fibrous

Cysts

Vascular

Melanocytic Nevi

Miscellaneous

ACNEIFORM ERUPTIONS . . . . . . . . . . . . . . . . . . 11

Acne Vulgaris/Common Acne

Rosacea

Perioral Dermatitis

DERMATITIS (ECZEMA) . . . . . . . . . . . . . . . . . . . 13

Contact Dermatitis

Atopic Dermatitis

Seborrheic Dermatitis

Stasis Dermatitis

Nummular Dermatitis

Dyshydrotic Dermatitis

Diaper Dermatitis

INFECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Bacterial

Superficial Skin (Epidermal)

Deeper Skin (Dermal)

Hair Follicles

Periungual Region

Sexually Transmitted Infections

Viral Infections

Dermatophytosis

Yeast

Parasitic

PAPULOSQUAMOUS DISEASES . . . . . . . . . . . . 25

Psoriasis

Psoriasis Arthritis

Lichen Planus

Pityriasis Rosea

VESICULOBULLOUS DISEASES . . . . . . . . . . . . . 28

Pemphigus Vulgaris

Bullous Pemphigoid

Dermatitis Herpetiformis (DH)

Porphyria Cutanea Tarda

Differential of Primary Bullous Disorder

MCCQE 2006 Review Notes

DRUG ERUPTIONS . . . . . . . . . . . . . . . . . . . . . . . . 30

Exanthematous Eruptions

Urticaria

Fixed Drug Eruption

Delayed Hypersensitivity Syndrome

Photosensitivity Eruptions

Serum Sickness - Like Reaction

ERYTHEMA MULTIFORME (EM), . . . . . . . . . . . 32

STEVENS-JOHNSON SYNDROME (SJS) AND

TOXIC EPIDERMAL NECROLYSIS (TEN)

ERYTHEMA NODOSUM . . . . . . . . . . . . . . . . . . . . 33

MALIGNANT SKIN TUMOURS . . . . . . . . . . . . . . 33

Basal Cell Carcinoma (BCC)

Squamous Cell Carcinoma (SCC)

Malignant Melanoma

Others

HERITABLE DISORDERS . . . . . . . . . . . . . . . . . . 36

Ichthyosis Vulgaris

Neurofibromatosis (NF)

Vitiligo

SKIN MANIFESTATIONS OF INTERNAL . . . . . 37

CONDITIONS

Autoimmune Disorders

Endocrine Disorders

HIV

Malignancy

Others

Pruritus

WOUNDS AND ULCERS . . . . . . . . . . . . . . . . . . . 39

ALOPECIA (HAIR LOSS) . . . . . . . . . . . . . . . . . . . 39

Non-Scarring (Non-Cicatricial) Alopecia

Scarring (Cicatricial) Alopecia

NAILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

TOPICAL THERAPY . . . . . . . . . . . . . . . . . . . . . . . . 41

Vehicles

Topical Steroids

Dry Skin Therapy

COSMETIC DERMATOLOGY . . . . . . . . . . . . . . . 43

Chemical Peel

Laser Therapy

SUNSCREENS AND PREVENTIVE . . . . . . . . . . . 43

THERAPY

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Dermatology – D1

APPROACH TO THE DERMATOLOGY . . . . . . . 2

PATIENT

History

Physical Exam

DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPROACH TO THE DERMATOLOGY PATIENT

HISTORY

age, race, occupation (especially exposures), hobbies

details of skin eruption should include:

• location, onset, duration (persistent versus intermittent eruption)

• alleviating and aggravating factors (plant contact, cosmetic/jewellery use,

exposure to heat/cold/sunlight, relationship to foods/spices)

• associated skin symptoms

• changes in sensation (itchiness, burning, pain)

• changes in surface (dryness versus discharge)

• past history including investigations and therapy

associated systemic symptoms (weight loss, malaise, fever, diarrhea, arthralgias, muscle weakness)

medications and allergies

past dermatological history

family history of atopy, skin cancer, psoriasis

PHYSICAL EXAM (How to describe a Lesion)

S ize

C olour (e.g. hyperpigmented, hypopigmented, erythematous)

A rrangement (e.g. solitary, linear, reticulated, grouped, herpetiform)

L esion morphology (see Table 2)

D istribution (e.g. dermatomal, intertriginous, symmetrical/asymmetrical, follicular)

Always check hair, nails, mucous membranes and intertriginous areas

Table 1. Skin Phototypes

Phototypes

Colour of Skin Without

Skin’s Response to Sun Exposure

Sun Exposure

White

Always burns, never tans

White

Always burns, little tan

III

White

Slight burn, slow tan

Pale Brown

Slight burn, faster tan

Brown

Rarely burns, dark tan

Dark brown/black

Never burns, dark tan

DEFINITIONS

PRIMARY MORPHOLOGICAL LESIONS

Table 2. Types of Lesions

< 1 cm Diameter

1 cm Diameter

Raised Superficial Lesion

Papule (e.g. wart)

Plaque (e.g. psoriasis)

Palpable Deep (dermal)

Nodule (e.g. dermatofibroma)

Tumour (e.g. lipoma)

Lesion (not necessarily raised)

Flat Lesion

Macule (e.g. freckle)

Patch (e.g. vitiligo)

Elevated Fluid-filled Lesions Vesicle (e.g. herpes simplex virus (HSV)) Bulla (e.g. bullous pemphigoid)

primary lesion : an initial lesion that has not been altered by trauma or manipulation, and has

not regressed

pustule : a vesicle containing purulent exudate (white, yellow, green)

cyst : a nodule containing semisolid or fluid material

erosion : a disruption of the skin involving the epidermis alone

ulcer : a disruption of the skin that extends into the dermis or deeper

wheal : a special form of papule or plaque that is blanchable and

transient, formed by edema in the dermis (e.g. urticaria)

scar : replacement fibrosis of dermis and subcutaneous tissue

SECONDARY MORPHOLOGICAL LESIONS

develop during the evolutionary process of skin disease, or are created by manipulation

or complication of primary lesion lesion (e.g. rubbing, scratching, infection)

crust : dried serum, blood, or purulent exudate originating from a lesion (e.g. impetigo)

scale : excess keratin (e.g. seborrheic dermatitis)

D2 – Dermatology

MCCQE 2006 Review Notes

DEFINITIONS . . . CONT.

fissure : a linear slit-like cleavage of the skin

excoriation : a scratch mark

lichenification : thickening of the skin and accentuation of normal

skin markings (e.g. chronic atopic dermatitis)

xerosis : dryness of skin, eyes and mouth

atrophy : histological decrease in size and number of cells or tissues

resulting in thinning or depression of the skin

OTHER MORPHOLOGICAL LESIONS

comedones : collection of sebum and keratin

• open comedone (blackhead)

• closed comedone (whitehead)

purpura : extravasation of blood into dermis resulting in

hemorrhagic lesions

• petechiae : small pinpoint purpura

• ecchymoses : large flat purpura

telangiectasia : dilated superficial blood vessels; blanchable

USEFUL DIFFERENTIAL DIAGNOSES

Table 3. Differential Diagnosis by Morphology

Dermatitis

Nondermatitis

(epidermal cells produced

Atopic Dermatitis (flexural folds)

Psoriasis (elbows/knees/scalp,

from excessive and

Nummular Eczema (coin-like, isolated)

Discoid Lupus (don’t see hair follicles)

abnormal keratinization

Seborrheic Dermatitis (scalp/nasolabial folds/chest)

Drug reaction (e.g. gold)

and shedding)

Lichen Planus (flat surface, lacy lines

on surface)

Mycosis Fungoides (girdle area, leonine facies)

Pityriasis Rosea (Christmas-tree distribution)

Secondary Syphilis (palms + soles,

copper coloured)

Tinea (well demarcated, raised border)

Inflammatory

Proliferative

Discrete Red Papules

Acne (teenager, face/chest/back)

Dermatofibroma (“dimple sign”)

(elevated/solid lesion < 1 cm)

Bites/Stings (history of outdoors, central punctum)

Hemangioma (blanching)

Folliculitis (in hair follicle)

Psoriasis

Furuncle (very painful, central plug)

Hives (whitish border, pruritic)

Inflamed Epidermal Cyst (mobile under skin)

Inflamed Seborrheic Keratosis (stuck-on appearance)

Lichen Planus (purple, polygonal papules with flat surface)

Miliaria Rubra (heat/overbundling of child)

Pyogenic Granuloma (bleeds easily)

Scabies (burrow, interdigital/groin, family members)

Urticaria

Flat Brown Macule

Actinic/Solar Lentigo (sun-damaged area)

(circumsrcibed flat and

Congenital Nevus (contain hair)

discoloured area)

Cafe-au-Lait (present in childhood, very light brown)

Hyper/hypopigmentation (e.g. posttraumatic, Addison’s)

Freckle (sun-exposed areas, disappears in winter)

Junctional Nevus (regular shape)

Lentigines associated with underlying disorders (LEOPARD, LAMB, Peutz-Jegher’s)

Lentigo Maligna (irregular, varied pigmentation)

Malignant Melanoma (characteristic atypia)

Pigmented Basal Cell Carcinoma

Simple Lentigo (non-sun exposed area, irregular)

Stasis Dermatitis

Viral

Nonviral

(circumscribed collection

• HSV (mouth, genitals)

Acute Contact Dermatitis (e.g. poison ivy)

of free fluid > 1 cm)

• Zoster (dermatomal,painful) Cat-Scratch Disease

• Varicella (generalized, itchy) Dyshydrotic Eczema (sides of fingers/palms/soles)

• Molluscum (umbilicated) Dermatitis Herpetiformis (VERY itchy, gluten history)

• Coxsackie Impetigo

(painful, hand-foot-mouth, summer) Porphyria Cutanea Tarda

(hypertrichosis, heliotrope lesion around eyes,

alcohol ingestion)

Scabies

Bullae

Bullous Impetigo (children, other family members)

(circumscribed collection

Bullous Pemphigoid (tense, lower limb)

of free fluid > 1 cm)

Drug eruption

EM/SJS/TEN (target lesions)

Lupus Erythematosus (American Rheumatology Association (ARA) criteria)

Pemphigus Vulgaris (flaccid, easy bleeding)

Poyphyria Cutanea Tarda (photodistribution, fragile skin, hyperpigmentation)

Dermatitis Herpetiforms (extensor surfaces, symmetrically grouped)

Acute dermatitis

MCCQE 2006 Review Notes

Dermatology – D3

Red Scaling Lesions

Contact Dermatitis (history)

nail pits, Koebner’s)

Vesicles

Viral

(exposure history)

USEFUL DIFFERENTIAL DIAGNOSES

. . . CONT.

Table 3. Differential Diagnosis by Morphology (continued)

Pustules

Acne (teenager, face/chest/back)

(elevated, contains

Acne Rosacea (forties, telangiectatic, no comedones)

purulent fluid,

Candida (satellite pustules, areas of skin folds)

varying in size)

Dermatophyte infection

Dyshidrotic Eczema (sides of fingers/palms/soles)

Folliculitis (in hair follicle)

Hidradenitis suppurativa

Impetigo (honey-crust)

Sepsis (e.g. staph, gonococcal)

Pustular Psoriasis (psoriasis)

Rosacea

Varicella

(break in the skin that extends

Common: Arterial, Venous, Neurotrophic, Pressure

to the dermis, or deeper)

Cancer (e.g. SCC),Chromosomal (e.g. XXY)

Hemoglobinopathy (e.g. Sickle Cell)

I nflammatory (e.g. RA, SLE, Vasculitis, Raynaud’s)

P yoderma Gangrenosum (e.g. ulcerative colitis, RA)

Infectious (syphilis, TB, tularemia, plague)

Necrobiosis Lipoidica Diabeticorum (DM)

Oral Ulcers

Aphthous

Cancer (SCC/BCC)

Dermatologic Diseases (Lichen Planus, Pemphigus vulgaris)

Iatrogenic (Chemo, Radiation)

Infectious (HSV/HZ, Coxsackie, HIV, CMV, TB, Syphilis, Aspergillosis, Cryptococcosis)

Inflammatory (SLE, Seronegatives, EM/SJS/TEN, allergic stomatitis)

Traumatic

Table 4. Differential Diagnosis by Location

Location

Common

Less Common and Rare

Scalp

psoriasis, folliculitis, pediculosis, tinea, SCC

Pemphigus, DH

Ears

Seborrheic dermatitis, psoriasis, infectious

Fungal infection

eczematoid dermatitis, actinic keratoses

Face

Acne, rosacea, impetigo, contact dermatitis,

Lupus, actinic dermatitis, dermatomyositis,

seborrheic dermatitis, folliculitis,

lentigo maligna melanoma

herpes simplex, BCC, SCC, actinic keratoses,

sebaceous hyperplasia

Eyelids

Contact dermatitis (fingernail polish, hairspray),

seborrheic dermatitis, atopic eczema,

xanthelasma

Posterior Neck

Neurodermatitis (LSC), seborrheic dermatitis, Acne keloidalis in black patients, acanthosis

psoriasis, contact dermatitis

nigricans

Mouth

Aphthae, herpes simplex, geographic tongue,

Syphilis, lichen planus, pemphigus

Axillae

Contact dermatitis, seborrheic dermatitis,

Erythrasma, acanthosis nigricans,

hidradenitis suppurtiva

inverse psoriasis, Fox-Fordyce disease

Chest and Back

tinea versicolour, pityriasis rosea, acne,

Secondary syphilis, Grover’s disease,

seborrheic dermatitis, psoriasis, Herpes Zoster

cherry angioma, BCC, melanoma

Crural Areas

psoriasis, pediculosis, granuloma inguinale,

lichen simplex

Penis

Contact dermatitis, fusospirochetal and Primary and secondary syphilis,

candidal balanitis, chancroid, herpes simplex, balanitis xerotica obliterans, lichen planus

Condylomata (HPV), scabies

Hands

Tinea manis, (one-hand two feet), warts,

erythema multiforme, secondary syphilis (palms)

atopic eczema, psoriasis, actinic

and fungal infection

keratosis, solar lentigo

Cubital Fossae and

Atopic eczema, contact dermatitis

Elbows and Knees

Psoriasis, xanthomas

Atopic ezcema, DH

Legs

Contact dermatitis, stasis dermatitis, ulcers,

leukocytoclastic vasculitis, HSP and other

vasculitidies

Feet

Fungal infection, primary or secondary

Psoriasis, erythema multiforme,

bacterial infection, contact dermatitis,

secondary syphilis (soles),

atopic eczema, warts

acral lentiginous melanoma (soles)

D4 – Dermatology

MCCQE 2006 Review Notes

Ulcer

Uncommon: “CHIP IN ” mnemonic

Seborrheic dermatitis, contact dermatitis,

contact dermatitis

Seborrheic keratosis, dysplastic nevi,

inverse psoriasis

Groin and

Tinea, Candida, bacterial intertrigo, scabies,

Contact dermatitis, dyshydrotic eczema,

Pustular psoriasis, granuloma annulare,

Popliteal Fossae

and prickly heat

nummular eczema, melanoma, ichthyosis

Pyoderma gangrenosum, erythema nodosum,

COMMON SKIN LESIONS

HYPERKERATOTIC

Seborrheic Keratosis (Senile Keratosis) (see Colour Atlas D8)

definition: benign neoplasm of epidermal cells

epidemiology

• > 30 years, M>F

• autosomal dominant inheritance

• more common with increasing age

differential diagnosis

• solar lentigo

• spreading pigmented actinic keratosis

• pigmented basal cell carcinoma

• malignant melanoma (lentigo maligna, nodular melanoma)

• melanocytic nevi

signs and symptoms

• round/oval, well demarcated discrete waxy papule/plaque, +/– pigment, warty surface,

“stuck on” appearance

• sites: face, trunk, upper extremities

• usually asymptomatic

clinical course

• over time, increase in pigmentation, “stuck on” plaque appears warty, “horny cysts”

investigations

• biopsy only if diagnosis uncertain

management

• no treatment usually needed

• liquid nitrogen for cosmetic reasons

Actinic Keratosis (Solar Keratosis) (see Colour Atlas D19)

definition: premalignant epithalial neoplasm

epidemiology

• middle age and elderly (except in sunny climates)

• M>F, skin phototypes I-III (see Table 1)

• melanin is protective

pathophysiology

• UV radiation damage to keratinocytes (especially UVB)

• pleomorphic keratinocytes, parakeratosis and atypical keratinocytes

differential diagnosis

• chronic cutaneous lupus erythematosus

• Bowen’s Disease

• SCC in situ

• superficial BCC

signs and symptoms

• discrete yellow-brown, scaly patches on a background of sun damaged skin (sand-like on palpation)

• < 1 cm, round/oval

• sites: areas of sun exposure - face (forehead, nose, cheeks,

lips, temples), ears, scalp if bald, neck, forearms, hands, shins

clinical course

• may transform into SCC

management

• 5-FU (fluorouracil) cream applied for 2-3 wks

• liquid nitrogen

• biopsy lesions that are refractory to treatment

Keratoacanthoma (see Colour Atlas D18)

definition

• benign epithelial neoplasm with atypical keratinocytes

epidemiology

• > 50 years, rare under 20 years

• skin phototypes I-III

etiology

• associated with human papilloma virus (HPV)

• associated with UV radiation and chemical carcinogens (tar, pitch, mineral oil)

pathophysiology

• proliferation of atypical keratinocytes in epidermis

differential diagnosis

• squamous cell carcinoma (SCC) (grows slower – months)

signs and symptoms

• red/skin coloured, firm, dome-shaped nodule with central keratin-filled crater

• sites: sun-exposed skin

clinical course

• rapidly grow to ~2.5 cm in 6 weeks, with keratotic plug in centre of nodule by 6 weeks

• attains full size in < 4 months,spontaneously regresses in < 10 months

• disfiguring scar after regression

management

• surgical excision

• curettage and electrocautery

• if on lip treat as SCC

MCCQE 2006 Review Notes

Dermatology – D5

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