PATHOMA19 - Skin Pathology Flashcards
What is the function of skin?
It is a barrier against environmental insults and fluid loss
What is skin composed of?
an epidermis and dermis
What is the epidermis comprised of?
keratinocytes and has four layers
What are the layers of the epidermis?
1) Stratum basalis 2) Stratum spinosum 3) Stratum granulosum 4) Stratum corneum
What is the stratum basalis?
regenerative (stem cell) layer
What is the stratum spinosum?
Its characterized by desmosomes between keratinocytes
What is the stratum granulosum?
It is characterized by granules in keratinocytes
What is the stratum corneum?
It is characterized by keratin in anucleate cells
What does the dermis consist of?
connective tissue, nerve endings, blood and lymphatic vessels, and adnexal structures (e.g., hair shafts, sweat glands, and sebaceous glands)
What are the inflammatory dermatoses?
1) atopic (eczematous) dermatitis 2) contact dermatitis 3) acne vulgaris 4) psoriasis 5) Lichen Planus
What is atopic (eczematous) dermatitis?
Pruritic, erythematous, oozing rash with vesicles and edema; often involves the face and flexor surfaces
What are flexor surfaces?
Elbow, wrists and knees
What is type 1 hypersensitivity reaction associated with?
asthma and allergic rhinitis
What is contact dermatitis?
Pruritic, erythematous, oozing rash with vesicles and edema
When does contact dermatitis arise?
upon exposure to allergens
What are the allergens for contact dermatitis?
1) Poison ivy and nickel jewelry (type IV hypersensitivity) 2) Irritant chemicals (e.g., detergents) 3) Drugs (e.g., penicillin)
What is the treatment for contact dermatitis?
It involves removal of the offending agent and topical glucocorticoids, if needed.
What is acne vulgaris?
Comedones (whiteheads and blackheads), pustules (pimples), and nodules; extremely common, especially in adolescents
What is acne vulgaris due to?
chronic inflammation of hair follicles and associated sebaceous glands
In acne vulgaris, how are comedones formed?
There is hormone-associated increase in sebum production (sebaceous glands have androgen receptors) and excess keratin production block follicles
What are propionibacterium acnes?
It is infection that produces lipases that break down sebum, releasing proinflammatory fatty acids; results in pustule or nodule formation
What is the treatment for acne vulgaris?
Treatment includes benzoyl peroxide (antimicrobial) and vitamin A derivatives (e.g., isotretinoin), which reduce keratin production.
What is psoriasis?
Well-circumscribed, salmon-colored plaques with silvery scale, usually on extensor surfaces and the scalp; pitting of nails may also be present.
What is psoriasis due to?
excessive keratinocyte proliferation
What is the etiology for psoriasis?
Possible autoimmune etiology
What is psoriasis associated with?
HLA-C
For psoriasis, what happens if there is an environmental trigger?
lesions often arise in areas of trauma (environmental trigger)
What does the histology for psoriasis show?
1) Acanthosis (epidermal hyperplasia) 2) Parakeratosis 3) Collections of neutrophils in the stratum corneum (Munro microabscesses) 4) Thinning of the epidermis above elongated dermal papillae; results in bleeding when scale is picked off (Auspitz sign)
What is parakeratosis?
hyperkeratosis with retention of keratinocyte nuclei in the stratum comeum
What is the treatment for psoriasis?
it involves corticosteroids, UV light with psoralen, or immune-modulating therapy.
What is lichen planus?
Pruritic, planar, polygonal, purple papules often with reticular white lines on their surface (Wickham striae); commonly involves wrists, elbows, and oral mucosa
What does lichen planus commonly involve?
Wrists, elbows and oral mucosa
What does oral involvement of lichen planus manifest as?
Wickham striae
What does histology for lichen planus show?
inflammation of the dermal-epidermal junction with a saw-tooth appearance
What is the etiology for lichen planus?
Etiology is unknown
What is lichen planus associated with?
chronic hepatitis C virus infection
What are the blistering dermatoses?
1) pemphigus vulgaris 2) bullous phemphigoid 3) dermatitis herpetiformois 4) erythema multiforme
What is pemphigus vulgaris?
Its autoimmune destruction of desmosomes between keratinocytes
What is pemphigus vulgaris due to?
IgG antibody against desmoglein (type II hypersensitivity)
What does pemphigus vulgaris present as?
skin and oral mucosa bullae
In pemphigus vulgaris, why is there suprabasal blisters?
Acantholysis (separation) of stratum spinosum keratinocytes (normally connected by desmosomes) results in suprabasal blisters.
In pemphigus vulgaris, why is there a tombstone appearance?
Basal layer cells remain attached to basement membrane via hemidesmosomes - tombstone appearance
In pemphigus vulgaris, why is there shallow erosions with dried crust?
Thin-walled bullae rupture easily (Nikolsky sign), leading to shallow erosions with dried crust.
In pemphigus vulgaris, why is there a fish net pattern?
Immunofluorescence highlights IgG surrounding keratinocytes in a fish net pattern.
What is bullous pemphigoid?
Autoimmune destruction of hemidesmosomes between basal cells and the underlying basement membrane
What is bullous pemphigoid due to?
Its due to IgG antibody against basement membrane collagen
What does bullous pemphigoid present as?
blisters of the skin, oral mucosa is spared 1) Basal cell layer is detached from the basement membrane 2) Tense bullae do not rupture easily; clinically milder than pemphigus vulgaris
In bullous pemphigoid, what does immunofluorescence show?
it highlights IgG along basement membrane (linear pattern)
What is dermatitis herpetiformis?
Autoimmune deposition of IgA at the tips of dermal papillae
What does dermatitis herpetiformis present?
as pruritic vesicles and bullae that are grouped (herpetiform)
Dermatitis herpetiformis has a strong association with what?
celiac disease; resolves with gluten-free diet
What is erythema multiforme?
Hypersensitivity reaction characterized by targetoid rash and bullae
What is the targetoid appearance due to?
central epidermal necrosis surrounded by erythema
Erythema multiforme is most commonly associated with what?
HSV infection
Aside form HSV infections, what do the other associations include?
Mycoplasma infection, drugs (penicillin and sulfonamides), autoimmune disease (eg SLE), and malignancy
What is Steven Johnsons syndrome?
EM with oral mucosa/lip involvement and fever is termed Stevens Johnson syndrome (SJS)
What is toxic epidermal necrolysis?
It is a severe form of SJS characterized by diffuse sloughing of skin, resembling a large bum; most often due to an adverse drug reaction