Chapter 19 Flashcards by Shane Hagen

What are the layers of the epidermis (composed of keratinocytes)?

Basalis- the regenerative stem cell layer
Spinosum- with desmosomes between keratinocytes
Granulosum- with granules in keratinocytes
Corneum

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What are the main components of the dermis?

CT, nerve endings, blood and lympatic vessels, and adnexal structures (e.g. hair shafts, sweat glands, and sebaceous glands)

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Describe atopic (eczematous) dermatitis

PRURITIC, erythematous oozing rash with vesicles and edema often involving the face and flexor surfaces

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What mediates atopic (eczematous) dermatitis?

type I rxn (associated with asthma and allergic rhinitis)

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Describe contact dermatitis

PRURITIC erythamatous oozing rash with vesicles and edema arising upon exposure to allergens such as poison ivy and nickel (type IV rxn), chemicals, and drugs

Tx: steroids

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What is acne vulgaris

Comedones (white and blackheads), pustules (pimples), and nodules due to chronic inflammation of HAIR FOLLICLES and associated sebaceous glands followed by a hormone-associated increase in sebum production (sebaceous glands have androgen receptors) and excess keratin

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What is the main source of the pustules and nodules associated with acne?

Propionibacterium acnes infection produces lipases that rbeask down sebum, releasing proinflammatory fatty acids

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What is psoriasis?

The formation of well-circumscribed, SALMON-COLORED plaques with a silvery scale, usually on the extensor surfaces and the scalp due to excessive keratinocyte prolfieration

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What are some suggested etiologies of psoriasis?

Possibly autoimmune (associated with HLA-C) or environmental (lesions often arise near trauma sites)

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Describe the histo of psoriasis?

Shows acenthsosis (epidermal hyperplasia)

Parakeratosis (hyperkeratosis with retention of keratinocyte nuclei in the stratum corneum)

Collections of neutrophils in the Stratum corneum (Munro microabscesses)

Epidermal thinning above elongated dermal papillae resulting in bleeding when scales are picked off (Auspitz sign)

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How is psoriasis tx?

steroids, UV light with psoralen, or immuno-modulation

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Describe lichen planus

A pruritic, formation of purple papules often with reticular white lines on their surface (Wickham striae)

commonly seen on the wrist, elbows, and oral mucosa

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What does the histo of lichen planus look like?

Inflammation of the dermal-epidermal junction with a ‘saw-tooth’ appearance

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What causes lichen planus?

Unknown but associated with HCV

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What causes pemphigus vulgaris?

Autoimmune destruction of DESMOSOMES between keratinocytes (IgG against desmoglein- type II rxn)

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Describe the histo of pemphigus vulgaris

Acantholysis (seperation) of the stratum spinosum keratinocytes resulting in suprabasal blisters

Basal layer cells remain attached to BM via hemidesmosomes (‘tombstone’ appearance)

Thin-walled bullae rupture (Nikolsky sign), leading to shallow erosions with dried crust

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Immunofluorescence of pemphigus vulgaris

Highlights IgG surrounding keratinocytes in a fish net pattern

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What is bullous pemphigoid?

Autoimmune destruction of the hemidesmosomes between basal cells and the underlying basement membrane due to IgG Ab against hemidesmosome components (BP180)

oral mucosa is commonly spared

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Describe the histo of bullous pemphigoid

Baslal cell layer detaches from the BM

Note that tense bullae do not rupture easily (clinically milder than pemphigus vulgaris)

Describe the immunoflourescence of bullous pemphigoid?

linear pattern of IgG along BM

What is dermatitis herptiformis?

Autoimmune deposition of IgA at the TIPS OF DERMAL PAPILLAE

presents as pruritic vesicles and bullae that are grouped (strong association with celiac disease)

Describe erythema multiforme (EM)

A hypersensitivity rxn marked by targetoid rash (due to central epidermal necrosis by erythema) and bullae

What are the major associations of erythema multiforme (EM)?

Most commonly HSV infection

also with Mycoplasma, drugs like penicillin/sulfonamides, autoimmune disease like SLE and malignancy

Seborrheic keratosis

benign squamous proliferation (common in elderly) presenting as raised, plaques (Sign of Leser-Trelat= GI malignancy)

What are the main risk factors for basal cell carcinoma?

UVB DNA damage including prolonged exposure to sunlight, albinism, and xeroderma pigmentosum Presents as an elevated nodule with a central, ulcerated crater surrounded by dilated (telangiectatic) vessels

Basal cell carcinomas are classically found where?

UPPER lip

Describe the histo of basal cell carcinoma

nodules of basal cells wwith peripheral palisading METS are rare

What causes squamous cell carcinoma?

malignant prolfieration of squamous cells marked by the formation of keratin pearls that presents as an ULCERATED, nodular mass, usually on the LOWER LIP

What dis?

Keratoacanthoma- well-differentiayed squamous cell carcinoma that develops rapidly and regresses spontaneously

\_\_\_\_\_\_\_\_ are responsible for skin pigmentation and are present where?

Melanocytes in the basal epidermis

Describe melanocytes

Derived from neural crest, and synthesize melanin in melanosomes using tyrosine as a precursor molecule (pass melanosomes to keratinocytes)

What is Vitiligo?

Localized loss of skin pigmentation due to autoimmune destruction of melanocytes

What causes albinism/

Enzyme defect (usually tyrosinase) that impaires melanin production

What is melasma?

Mask-like hyperpigmentation of the cheeks commonly associated with pregnancy and oral contraceptives

What is the most important prognostic feature of melanoma?

**Breslow thickness**- depth of extension into the dermis

What are the main variants of melanoma?

1. **Superficial spreading**-most common; dominant early radical growth results in GOOD prognosis 2. Lentigo maligna melanoma- good prognosis 3. Nodular- early verticle growth; poor prognosis 4. Acral lentiginous-arises on palms/soles, often in dark-skinned people and not related to UV exposure

Lentigo maligna melanoma

Nodular melanoma

Acral lentiginous melanoma

What are the most common causes of impetigo, a superficial bacterial skin infection?

S. aureus or S. pyogenes

Describe cellulitis

Deeper (dermal) infection, usually due to S. aureus and S. pyogenes presenting as a red, tender rash with fever that can progress to necrotizing fasciitis

Describe Staphylococcal Scalded Skin Syndrome

Sloughing of skin due to S. aureus exfoliative A and B toxins resulting in epidermolysis of the straum granulosum

How is SSSS distinguished from TEN?

TEN seperation at the dermal-epidermal junction

What is this?

Rosacea is a long term skin condition characterized by facial redness, small and superficial dilated blood vessels on facial skin, papules, pustules, and swelling.[2] Rosacea typically begins as redness on the central face across the cheeks, nose, or forehead, but can also less commonly affect the neck, chest, ears, and scalp.[3] In some cases, additional signs, such as semipermanent redness, dilation of superficial blood vessels on the face, red domed papules(small bumps) and pustules, red gritty eyes, burning and stinging sensations, and in some advanced cases, a red lobulated nose (rhinophyma), may develop. Rosacea affects all ages and has four subtypes, three affecting the skin and the fourth affecting the eyes (ocular rosacea). Rosacea is almost three times more common in women. It is commonly found in people between the ages of 30 and 50, and is more common in Caucasians.[2] Treatment has typically been with doxycycline, tetracycline, or metronidazole. Other treatments with tentative benefit include brimonidine cream, ivermectin cream, and isotretinoin

What is this?

Molluscum Contagiosum- due to poxvirus and most commonly arising in children (also can occur ins exually active adults and immunocompromised pts.)

What is a classic histo finding of Molluscum Contagiosum?

Molluscum bodies