Derm pathophys

Can all skin diseases be observed clinically?

mhm. yep. yeah. they can.

list the functions of the skin

maintain normal body temp

protective barrier against invading organisms, UV, and trauma

receive external sensory stimuli

control insensible water loss

How is skin distinct from mucosa?

contains adnexal structures, such as eccrine units that exude sweat and folliculosebaceous units that produce hair/oils

If you look into a light microscope and see stratified squamous epithelium, what layer are you looking at?

epidermis

If you look into a light microscope and see a layer of connective tissue, what layer of skin are you looking at?

dermis

Describe the epidermis

outermost layer that is superficial, tough, protective, made up of stratified epithelium that contains keratinocytes, melanocytes, has 5 layers, and is where exocrine sweat glands open

What is the undulating, basement membrane and epidermal junction that separates the epidermis from the dermis?

dermal layer (basal)

Describe the dermis

semi-fluid layer that binds the body together and contains nerve endings, oil/sweat glands, hair follicles, blood/lymph vessels, connective tissue, is where tattoos are and is not regenerative like the epidermis

What layer of the epidermis has anucleate, flattened keratinocytes?

cornified layer

What layer of the epidermis has cells w/ cytoplasmic granularity resulting from an accumulation of keratin complexes? (is also where skin heals/new skin grows)

granular layer

What layer of the epidermis has cells w/ ample cytoplasm and prominent desmosomes?

spinous layer

What layer of the epidermis has cuboidal germinative keratinocytes?

basal layer

What are the layers of the epidermis?

stratum corneum, (stratum lucideum), stratum granulosum, stratum spinosum, , stratum basale (dermal layer)

What is an intercalated dendritic cell in the basal layer that provides a dispersed screen against UV rays?

melanocyte

What is an intercalated dendritic cell that is bone marrow-derived and antigen presenting?

langerhans cells

What layer consists of connective tissue gel, collagen types I and II, and elastic microfibrils, and serves as the scaffolding that supports complex neurovascular networks?

dermis

What cells are in the dermis?

fibrocytes, mast cells, dendritic immune cells

What are the three types of skin diseases?

inflammatory, infectious, neoplastic

What is a macule?

area of increased or decreased pigmentation w/o elevation or depression

less than 1 cm, not palpable, superficial layers only

What is a patch?

macular type lesion that is flat, circumscribed and greater than 1cm

What is a papule?

superficial, solid lesion less than 1 cm, often occurs in clusters, and can accompany rashes

What may cause a papule?

inflammation from infected/abraded skin, accumulated secretions, infections such as disseminated histoplasmosis, hypertrophy of skin cells, acne

What is a plaque?

plateau-like elevation w/ a surface area greater than its height;

greater than 1 cm in size and frequently forms by confluence of papules

characterized by lichenification

What is lichenification?

rough and thickened skin that accentuates normal skin lines and resembles tree bark

What disorders is lichenificaiton associated with?

pruritic disorders; chronic eczema, atopic dermatitis

What is a vesicle?

small, circular, fluid filled lesion on or below the skin

less than 1 cm

What is bulla?

circumscribed collection of free fluid greater than 1 cm

What is a pustule?

superficial skin cavity containing purulent exudate; may be yellow, white, green-white, or hemorrhagic

(vesicle or bulla containing purulent fluid)

What would you call a vesicle or bulla that contains purulent fluid?

pustule

What is a blister?

both vesicles and bulla; defense mechanism of body where epidermis separates from the dermis and a pool of lymph and other fluids collect between the layers while skin regrows from underneath

What is etiology for blisters?

chemical or allergic rxn, physical injury (heat, frostbite, friction)

What is a nodule?

solid, circular lesion greater than 1 cm that usually invades epidermis and lower dermis

What is another name for a wheal?

urticarial exanthema, urticaria

What is a wheal?

rounded or flat topped edematous plaque that is well demarcated; no scaling or epidermal involvement, color and shape varies

What shape can wheals be?

round, oval, gyrate, annular or serpiginous

What causes wheals?

allergic response

What is darier’s sign?

gentle rubbing or stroking of lesions is followed by local itching, erythema, and wheal formation w/in 2-5 min

What is dermatographism?

“writing on the skin”; very common localized hive reaction

What is a cyst?

elevated, circumscribed and palpable encapsulated lesion filled w/ fluid or semisolid material /

enclosed sac w/ distinct membrane lining

What is an abscess?

collection of pus

What is crust?

dried serum or exudates on skin surface; present after blisters rupture

What color does crust from dried blood appear?

brown

What color does crust from dried serum appear?

honey colored

What color does crust from dried pus appear?

yellow-green

What are scales/ desquamation?

abnormal areas of stratum corneum, may be adherent or loose, large sheet like areas or tiny particles that peel

caused by inc rate of epidermal cell proliferation

What is an erosion?

skin defect with loss of epidermis only and heals WITHOUT a scar

What is an ulcer?

skin defect with loss of epidermis and upper layer of dermis; always heals WITH scar tissue

what are telangiectasis?

small enlarged blood vessels near surface of skin often nose, cheeks, and chin; usually only mms in size; sign of chronic alcoholism

What is petechiae?

small red or purple spots on the body, less than 3 mm, caused by minor hemorrhage (broken cap), thrombocytopenia, or dec platelet function

What is purpura?

larger red or purple discolorations on the skin, 3-10mm in size, caused by bleeding under the skin

What is ecchymosis?

capillary damage that allows blood to extravasate into surrounding tissues, greater than 1 cm, usually caused by blunt trauma

Do petechiae, purpura, and ecchymosis blanch with pressure? (disappear when you push on them)

sir no sir

What is a tumor?

solid lesion w/ elevation and depth, usually involves epidermis and dermis (possible SC), greater than 2 cm, and ± pigmentation

What is a serpiginous lesion?

irregular / wavy / snake like pattern (ex: hookworm)

What does zosterform mean when describing lesions?

only affects a specific dermatome

How many distinct patterns of dermatitis are there?

9

hives is an example of what pattern of inflammatory disease?

perivascular dermatitis

What is perivascular dermatitis?

perivascular inflammatory infiltrate w/o significant epidermal involvement

allergic contact dermatitis is an example of what pattern of inflammatory disease?

spongiotic dermatitis

What is spongiotic dermatitis?

associated with intercellular epidermal edema (spongiosis)

psoriasis is an example of what pattern of inflammatory disease?

psoriasiform dermatitis

What is psoriasiform dermatitis?

associated w/ epidermal thickening from elongated rete ridges

lichen planus is an example of what pattern of inflammatory disease?

interface dermatitis

what is interface dermatitis?

cytotoxic rxn that affects dermis and epidermis characterized bt vacuoles and lymphocyte infiltrates

bullous pemphigoid is an example of what pattern of inflammatory disease?

vesiculobullous dermatitis

what is vesiculobullous dermatitis?

intradermal or subepidermal cleavage

leukocytoclastic vasculitis is an example of what pattern of inflammatory disease?

vasculitis

what is vasculitis?

damage to cutaneous vessel walls

acne folliculitis is an example of what pattern of inflammatory disease?

folliculitis

What is folliculitis?

rxn directed against colliculo-sebacous units

cutaneous sarcoidosis is an example of what pattern of inflammatory disease?

nodular dermatitis

what is nodular dermatitis?

nodular or diffuse dermal infiltrate w/o significant epidermal changes

erythema nodusum is an example of what pattern of inflammatory disease?

panniculitis

what is panniculitis?

involves SC fat

What is the clinical presentation of psoriasis?

sharply marginated, erythematous, and surmounted by silvery scales

What is most common age of onset for psoriasis?

third decade (equal in sexes and ethnic groups)

what is etiology for psoriasis?

unknown, likely multifactorial inherited condition; FMHx is common

what is squirting dermal papillae? What disorder is it seen in?

migration of neutrophils from dermal papillae into overlying epidermis;

psoriasis

Besides silvery scales, what else is seen in psoriasis?

epidermal hyperplasia (thicker skin), changes in rete ridges, thinning of suprapapillary plate, squirting dermal papillae, and inflammatory cells in the epidermis

What surfaces are spared from psoriasis?

mucosal surfaces

what surfaces are often involved in psoriasis?

scalp, extensor surfaces of extremities, flexural surfaces, nails

what is the only extracutaneous manifestation of psoriasis?

psoriatic arthritis

What is psoriatic arthritis?

deforming, asymmetric (1 joint), oligoarticular arhtritis that can involve small or large joints; classified as seronegative spondyloarthropathy

what joints are characteristically involved in psoriatic arthritis?

distal interphalangeal joints of fingers and toes

What happens with lymphocytes in interface dermatitis?

they attack the basal/dermal layer of epidermis causing vacuolar change in the basal cells or necrosis of basal keratinocytes

What is an example of chronic interface dermatitis?

lichen planus

What is an example of acute interface dermatitis?

erythema multiforme

Describe the pathophysiology of many of the diseases in interface dermatitis

T cell mediated damage to keratinocytes and remodeling of the basement membrane zone;

injury to basal keratinocytes and other structures produces tiny vacuoles along the dermoepidermal junction on both sides of basal lamina (vacuolization or liquefaction degeneration)

Is lichen planus more common in men or women?

women

etiology of lichen planus

mostly unknown but drugs such as therapeutic gold and antimalarial agents are shown to play a role

pathogenesis of lichen planus

begins w/ dense infiltrate of T cells in papillary and superficial dermis, keratinocytes and melanocytes become damaged, vacuoles and colloid bodies appear in lower dermis, and mature lesions are composed of CD8 cytotoxic T cells

What are the PE findings of lichen planus?

pruritic polygonal violaceous (purple) flat topped papules w/ wickham’s striae (minute whitish streaks); usually bilateral and symmetric

solitary lesions combine to form larger plaques

Where are common sites for lichen planus?

flexor surfaces of extremities, genital skin, mucous membranes

When do peak incidences of erythema multiforme happen?

2nd-4th decade of life (equal in men and women)

What is erythema multiforme?

cell mediated immune rxn that results in necrosis of epidermal keratinocytes; example of acute interface dermatitis

What is etiology for erythema multiforme?

HSV, rxn to meds, idiopathic

What are PE findings of erythema multiforme?

acute cutaneous eruption to skin or mucous membranes that is benign and self limited

lesions develop in crops on acral surfaces (affects distal portions of limbs);

monomorphous pattern- red macule o thin papule that expands from center outward, center becomes dusky or necrotic appearing “target-like”

What is EM minor?

scattered lesions w/ limited mucosal involvement

What is EM major?

prominent involvement in at least 2-3 mucosal sites (oral, anogenital, conjunctival); encompasses Steven-johnson syndrome and toxic epidermal necrolysis

What is the pathogenesis of erythema multiforme?

sparse inflammatory infiltrate leads to necrosis of keratinocytes and creates widely distributed vacuolated keratinocytes;

CD4 & CD8 compose the infiltrate

target like appearance reflects zones of inflammatory rxn and damage