B3-Dermatology

Derm definitions

Macule

small circumscribed area of change in skin color w/o elevation or depression

Papule

small solid, elevated lesion which projects above the plane of surrounding skin

Nodule

large, solid elevated lesion

Patch

large, non-elevated area of skin with a different color than the surrounding area

Plaque

large plateau-like elevation above the skin

Vesicle

small circumscribed, elevated, superficial cavity of fluid

Bulla

large circumscribed, elevated, superficial cavity of fluid

Pustule

circumscribed superficial cavity of skin that contains a purulent exudate which may be yellow

Wheal

a rounded or flat-topped pale papule/plaque that disappears in 48 hours; due to edema of the dermis

Scale

secondary skin change; flakes of the stratum corneum

Lichenification

thickening of the epidermis with deepening of skin lines in parallel or rhomboidal pattern

Crust

Develop when serum, blood, or pus dries on skin surface

Eczematous dermatitides

polymorphic inflammatory reaction pattern involving the epidermis and dermis that is red, itchy, and has surface change

Stratum spinosum

Hyperplasia of what skin layer occurs during eczematous dermatitides?

Spongeosis

intracellular edema in the epidermis

Atopic Dermatitis

elevated serum IgE (type 1 HS), activated T cells in the dermis cause red, patchy, itchy skin

Allergic contact dermatitis

cell mediated HS (type IV) that requires prior sensitization to a chemical

Primary Irritant Dermatitis

direct irritation that is non-immunologic

Drug related eczematous dermatitis

caused by drugs that effect the skin barrier or lead to immunologic response (statins, immune modulating drugs)

Seborrheic dermatitis

common, seen in areas with the most sebaceous glands, may present with dandruff or cardle cap

Parkinsons & HIV/AIDs

What population has an increased incidence of seborrheic dermatitis?

Psoriasis

chronic disorder with a polygenic predisposition that affects 1.5-2% of population

Koebner phenomenon

appearance of new skin lesions on areas of cutaneous injury

Auspitz sign

Pinpoint bleeding spots from exposure of dermal papillae

Lichen planus

papule, purple, polygonal, pruritic; arms and legs as well as while papules in the mouth

Saw tooth ridges

Wickham’s striae

Fine white lines on surface of papules of plaques in lichen planus

Acne rosacea

inflammation of pilosebaceous units, cause redness and pustules but no comedones

Mastocytosis

increased mast cells in the skin

Darier sign

lesions become red and raised when stroked due to mast cell degranulation

dermatographism

stroking normal skin with a pointed instrument causes degranulation and hives resembling shape drawn

mycosis fungoides

lymphoma of CD4+ T helper cells

develops from flat to plaque to nodule

Pemphigus Vulgaris

Intraepidermal/suprabasal bullous disease

Bullous pemphigoid

Dermatitis herpetiformis

Subepidermal bullous disease

Desmosomes

cell to cell attachments between the epithelial cells of the epidermis

Hemidesmosomes

attach basal cells to the basement membrane (epidermis to basement membrane)

Anchoring fibrils

type 7 collagen that anchors the hemidesmosomes/basement membrane to the dermis

Pemphigus Vulgaris

autoantibodies against desmogleins (3 or 3/1) which disrupt the attachments and result in acantolysis

would expect to find a blister ABOVE the basal cell layer

IgG deposition along cell membranes (light green immunofluorescence) showing loss in cell to cell adhesion

*Nikolsky Sign

Tx: corticosteroids

Nikolsky Sign

slight rubbing/pressure produces exfoliation of the outermost layer of skin

Dermatitis Herpetiformis

IgA transglutaminase autoantibodies bind reticulin (anchoring fibril) so that the epidermal basement membrane is no longer anchored to the dermis

Granular IgA deposits in dermal papillae causing inflammation

Almost everyone with dermatitis herpetiformis also has CROHNS DISEASE

strikingly bilateral lesions

tx: dapsone and gluten free diet

Bullous pemphigoid

TENSE bullae w/ epidermis that remains intact

antibodies against BPAGs which are components of hemidesmosomes (*BPAG2/BP180)

subepidermal, nonacantholytic blisters w/ entire epidermis in the root

eosinophils

linear IgG deposition along dermoepidermal junction *involves complement activation