Pathoma - Skin Pathology

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stratum basalis contents

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regenerative stem cell layer

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stratum spinosum contents

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desmosomes between keratinocytes

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stratum granulosum contents

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granules in keratinocytes

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stratum corneum contents

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keratin in anucleate cells

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dermis contents

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connective tissue, nerve endings, blood and lymphatic vessels, hair shafts, sweat glands, and sebaceous glands

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atopic dermatitis clinical findings

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pruritic, erythematous, oozing rash with vesicles and edema involving face and flexor surfaces

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atopic dermatitis type of reaction

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type I hypersensitivity reaction

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atopic dermatitis associations

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allergic rhinitis and asthma

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contact dermatitis clinical findings

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pruritic, erythematous, oozing rash with vesicles and edema

arises upon exposure to allergens

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irritants see in contact dermatitis

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poison ivy and nickel jewelry (type IV hypersensitivity reacion), detergents, drugs

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acne vulgaris lesions

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comedone, pustules, nodules (scarring)

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cause of acne vulgaris

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chronic inflammation of hari follicles and associated sebaceous glands
1. hormone associated increase in sebum production and excess keratin production block follicles, forming comedones
2. propionibacterium acnes infection produces lipases that break down sebum, releasing proinflammatory fatty acids which results in pustule or nodule

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treatment of acne

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vitamin A derivatives which reduce keratin production and antimicrobial benzoyl peroxide

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clinical presentation of psoriasis

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well-circumscribed salmon-colored plaques with silvery scale usually on extensor surfaces and scalp; pitting of nails may also be present

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cause of psoriasis

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due to excessive keratinocyte proliferation

possibly autoimmune, associated with HLA-C, and can arise in areas of trauma

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histological findings in psoriasis

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1. acanthosis
2. parakeratosis
3. collections of neutros in corneum
4. thinning of epidermis above elongated dermal papillae resulting in pin point bleeding when scale is picked off

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acanthosis

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epidermal hyperplasia (psoriasis)

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parakeratosis

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

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munro microabscesses

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collections of neutrophils in stratum corneum (psoriasis)

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auspitz sign

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pin point bleeding when scale is picked off (psoriasis)

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treatment of psoriasis

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corticosteroids, UVA light with psoralen, immune-modulating therapy

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lichen planus P's

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pruritic, planar, polygonal, purple papules

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wickham striae

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reticular white lines on surface in lichen planus

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locations in lichen planus

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wrists, elbows, oral mucosa

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lichen planus associations

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hepatitis C

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what is pemphigus vulgaris

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autoimmune destruction of desmosomes between keratinocytes

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what causes pemphigus vulgaris

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due to IgG antibody against desmoglein (type II hypersensitivity)

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clinical presentation of pemphigus vulgaris

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1. acanthosis of spinosum keratinocytes
2. basal layer still attached to basement membrane via hemidesmosomes giving tombstone appearance
3. thin-walled bullae rupture easily leading to shallow erosions with dried crust
4. immunofluorescence highlights IgG surrounding keratinocytes in a fish net pattern

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what is bullous pemphigoid

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autoimmune destruction of hemidesmosomes due to IgG antibody against basement membrane

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presentation of bullous pemphigoid

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subepidermal blisters of skin that spares oral mucosa; has tense bullae that does not rupture easily

immunofluorescence highlights IgG along basement membrane in linear pattern

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what is dermatitis herpetiformis

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autoimmune deposition of IgA at tips of dermal papillae

this IgA are antibodies against gluten that cross react with reticulin fibers connecting epidermis to basement membrane

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clinical presentation of dermatitis herpetiformis

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pruritic vesicles and bullae that are grouped

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dermatitis herpetiformis association

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celiac disease

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what is erythema multiforme

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hypersensitivity reaction characterized by targetoid rash and bullae; targetoid is due to central epidermal necrosis surrounded by erythema

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erythema multiforme associations

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HSV
also: mycoplasma, drugs, autoimmune, malignancy

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clinical presentation of erythema multiforme and oral mucosa and lip involvement with fever

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steven-johnson syndrome

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toxic epidermal necrolysis

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severe form of SJS characterized by diffuse sloughing of skin, resembling large burn and is most often due to adverse drug reaction

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what is seborrheic keratosis

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benign squamous proliferation that is common in elderly

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clinical presentation of seborrheic keratosis

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raised, discolored plaques on extremities or face that often has a coin like, waxy, 'stuck on' appearance

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characteristic histological sign in seborrheic keratosis

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keratin pseudocysts

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leser-trelat sign

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sudden onset of multiple seborrheic keratoses that suggests underlying carcinoma of the GI tract

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what is acanthosis nigricans

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epidermal hyperplasia with darkening of the skin (velvet-like skin) that often involved axilla or groin

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acanthosis nigricans associations

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insulin resistance and malignancy (especially gastric carcinoma)

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most common cutaneous malignancy

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basal cell carcinoma

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risk factors of basal cell carcinoma

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prolonged exposure to sunlight, albinism, and xeroderma pigmentosum

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xeroderma pigmentosum and its association with basal cell carcinoma

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sunlight hits DNA and forms pyrimadine dimers which usually are excised by nucleotide excision repair pathway. in XP, this autosomal recessive dysfunction of enzymes in this pathway can cause basal cell carcinoma

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basal cell carcinoma presentation

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elevated nodule with a central, ulcerated crater surrounded by dilated blood vessels
(think pink pearl-like papule)

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classic location of basal cell carcinoma

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upper lip

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histological findings of basal cell carcinoma

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nodules of basal cells with peripheral palisading

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treatment of basal cell carcinoma

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surgical excision; metastasis is rare; prognosis is excellent

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risk factors of squamous cell carcinoma

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sunlight, albinism, xeroderma pigmentosum, immunosuppressive therapy, arsenic exposure, chronic inflammation

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clinical presentation of squamous cell carcinoma

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ulcerated, nodular mass usually on face

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classic location of squamous cell carcinoma

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lower lip

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actinic keratosis

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precursor lesion of squamous cell carcinoma and presents as hyperkeratotic, scaly plaque on face, back, or neck

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keratoacanthoma

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well-differentiated squamous cell carcinoma that develops rapidly and regresses spontaneously; presents as cup-shaped tumor filled with keratin debris

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melanocytes characteristics

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in basal layer, derived from neural crest, take tyrosine as precursor molecule and make melanin in melanosomes which pass to keratinocytes

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vitiligo

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localized loss of skin pigmentation due to autoimmune destruction of melanocytes

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albinism cuase

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congenital lack of pigment due to enzyme defect (usually tyorsinase) that impairs melanin production

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types of albinism

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ocular and oculocutaneous forms

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freckle

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small, tan-brown macule that darkens when exposed to sunlight due to increased numbers of melanosomes

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melasma

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mask-like hyperpigmentation of cheeks associated with pregnancy and oral contraceptive pills

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nevus (mole)

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benign neoplasm of melanocytes

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characteristic of nevus

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hair growing from it

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progression of acquired nevus

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1. begins as a nest of melanoytes at the dermal-epidermal junction (junctional- most common in children)
2. grows by extension into the dermis (compound)
3. junctional component lost resulting in intradermal (most common in adults)

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clinical presentation of nevus

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flat macule or raised papule with symmetry, sharp borders, evenly distributed color, and small diameter

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most common cause of death from skin cancer

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melanoma

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dysplastic nevus syndrome

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autosomal dominant disorder characterized by formation of dysplastic nevi that may progress to melanoma

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ABCDEs of melanoma

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Asymmetry, Border, Color, Diameter, Evolution

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growth phases of melanoma

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1. radial, horizontal along epidermis and superficial dermis (low risk of metastasis)
2. vertical growth into the deep dermis (increased risk of metastasis)

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most important prognostic factor in predicting metastasis in melanoma

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breslow thickness- depth of extension

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variants of melanoma

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1. superficial spreading
2. lentigo maligna melanoma
3. nodular
4. acral lentiginous

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superficial spreading melanoma

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most common subtype; dominant early radial growth results in good prognosis

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lentigo maligna melanoma

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lentiginous proliferation (radial growth) along junction; good prognosis

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nodular melanoma

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early vertical growth that pushes epidermis up which causes nodule formation; poor prognosis

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acral lentiginous melanoma

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arises on palms or soles, often in dark-skinned patients, not related to UV light exposure

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impetigo

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superficial bacterial skin infection due to staph aureus and strep pyogenes that commonly affects children

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presentation of impetigo

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erythematous macules that progress to pustules usually on face; ruptures results in erosions and dry, crusted, honey-colored serum

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cellulitis

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deeper (dermal and subQ) infection, usually due to staph aureus and strep pyogenes

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clinical presentation of cellulitis

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red, tender, swollen rash with fever

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risk factors for cellulitis

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trauma, surgery, insect bite

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cellulitis can progress to...

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necrotizing fascitis with necrosis of subQ tissue due to infection with anaerobic flesh eating bacteria(production of carbon dioxide leads to crepitus)

this is a surgical emergency

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clinical presentation of staphylococcal scalded skin syndrome

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sloughing of skin with erythematous rash and fever; leads to significant skin loss

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what is staphylococcal scalded skin syndrome

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due to staph aureus infection producing exfoliative A and B toxins in epidermolysis of the stratum granulosum

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verruca

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wart
-flesh-colored papules with rough surface

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cause of verruca

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HPV infection of keratinocytes

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location of verruca

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hands and feet

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molluscum contagiosum

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firm, pink umbilicated papules due to poxvirus

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hallmark of molluscum contagiosum

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molluscum bodies: viral cytoplasmic inclusions

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verruca keratinocyte changes

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koilocytic change

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virus implicated in molluscum contagiosum

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poxvirus

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people with molluscum contagiosum

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children, sexually active adults, and immunocompromised individuals