Skin Pathology: Inflammatory Dermatoses Flashcards Preview

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Flashcards in Skin Pathology: Inflammatory Dermatoses Deck (16):
1

What causes dermatitis? How does it generally present? What do we call this presentation?

- dermatitis is largely an overreaction of the body's innate immune system
- generally presents as eczema (basically synonymous with dermatitis): pruritic, erythematous, weeping, peeling, and blistering lesions

2

What are the major acute inflammatory dermatoses? Chronic inflammatory dermatoses?

- acute (minutes to weeks): urticaria (hives), contact dermatitis, atopic dermatitis, erythema multiforme
- chronic (months to years): psoriasis, lichen planus

3

What is urticaria and what is it due to? What is it commonly known as? How do we treat it?

- (an acute inflammatory dermatitis)
- urticaria is the sudden breakout of erythematous, edematous, pruritic plaques called wheals; migratory dermal edema
- due to localized mast cell degranulation via IgE (it is an immediate AKA type I hypersensitivity reaction), which triggers the superficial dermis to swell (dermal edema) and raise the epidermis
- it is known as hives
- treat with antihistamines

4

What is allergic contact dermatitis and what is it due to? How do we treat it?

- (an acute inflammatory dermatitis)
- contact dermatitis is essentially a type of acute eczematous dermatitis (pruritic, erythematous, oozing rash with vesicles and edema)
- it is due to an allergic delayed AKA type IV hypersensitivity reaction with an induction and an elicitation phase
- (this is what happens with poison ivy)
- treat with topical corticosteroids or topical calcineurin inhibitors

5

Other than the allergic type, what other types of contact dermatitis are there?

- irritant contact: no prior sensitization is required, substance simply irritates the skin to the point of causing inflammation
- photo contact: certain substances applied to skin react with UV radiation and elicit and inflammatory response

6

What is atopic dermatitis and what is it due to? Where does it usually occur? How do we treat it? What is it associated with?

- (an acute inflammatory dermatitis)
- atopic dermatitis is a condition of intermittent flare-ups of eczema (pruritic, erythematous, oozing rash with vesicles and edema)
- it is due to an immediate AKA type I hypersensitivity reaction
- usually occurs on flexor surfaces, and commonly involves the face in children
- treat with topical corticosteroids or topical calcineurin inhibitors
- it is highly associated with asthma and allergic rhinitis (the three together are known as the atopic triad)

7

What is atopy?

- atopy is an immune bias towards TH2 helper T cells, which favor IgE and extracellular eradication (vs. TH1 helper T cells, which favor IgG and intracellular eradication)
- this IgE favoring results in an increased likelihood of causing mast cell degranulation via IgE cross-linking
- occurs in urticaria, atopic dermatitis, asthma, and allergic rhinitis

8

What is erythema multiforme? What is it caused by? How do we treat it?

- (an acute inflammatory dermatitis)
- erythema multiforme is a hypersensitivity reaction resulting in the breakout of macules, papules, vesicles, bullae, and the characteristic targetoid lesions (this multiple presentation is where "multiforme" comes from)
- it is uncommon, but is caused by a reaction to infection and/or drugs (major culprits are HSV and penicillin)
- it is self-limiting, so management is usually supportive
- *can develop into life-threatening SJS or TEN*

9

What can erythema multiforme progress into?

- (occurs due an adverse drug reaction)
- can progress into a life-threatening form known as Stevens-Johnson Syndrome (SJS) or an even worse form known as Toxic Epidermal Necrosis (TEN)
- these conditions are characterized by oral mucosal involvement, fever, and the sloughing off of large portions of skin (resembles a severe burn), which can cause fluid loss and infection
- SJS has a 5-10% mortality rate
- TEN has a 30% mortality rate

10

What is psoriasis? What is the supposed major genetic component and environmental trigger? What is the Koebner phenomenon? How do we treat psoriasis?

- (a chronic inflammatory dermatitis)
- psoriasis is a common (1-2% of U.S. population) supposed autoimmune disorder resulting in the hyperproliferation of the epidermal keratinocytes (turn-over rate goes from 22 days to 3-5 days)
- the lesions are characteristically well-circumscribed, pink/salmon colored plaques with loosely adhered silvery scales; commonly affects the extensor surfaces
- supposed genetic component: HLA-C
- environmental trigger: trauma, scarring, tattoos (this is known as the Koebner phenomenon, which mainly relates to trauma)
- treat with topical corticosteroids, topical calcineurin inhibitors, methotrexate, biologicals, UV phototherapy/vitamin D analogs

11

What morphologies does the extreme keratinocyte hyperproliferation seen in psoriasis result in? What is Auspitz sign?

- the hyperproliferation results in downward elongation of the epidermal rete ridges of the basement membrane (gives a characteristic "test tubes in a rack" appearance)
- obliterates the stratum granulosum
- causes parakeratosis (the keratinocytes of the corneal layer retain their nuclei)
- actually THINS the epidermis just above the dermal papillary tips; since the papillae hold the capillaries supplying the epidermis, scratching the psoriatic lesions will result in pin-point bleeding (this is called Auspitz sign)

12

Which parts of the body are mainly involved in psoriasis? 30-50% of patients with psoriasis will also have changes to what part of the body? What major complication may occur in patients with psoriasis?

- mainly affects: *extensor surfaces (with elbows, knees) and scalp*, gluteal clefts, umbilicus, and genitals
- 30-50% will also have nail changes due to the psoriasis
- psoriatic arthritis (a seronegative spondyloarthropathy associated with HLA-B27) may develop in up to 30% of patients; it classically affects the DIP joints of fingers and toes

13

What is lichen planus? What characteristic histological morphology is seen? What are Wickham striae?

- (a chronic inflammatory dermatitis)
- lichen planus is uncommon; characterized by "pruritic, purple (violaceous), polygonal, planar papules and plaques"
- due to an immune response against the epidermal-dermal junction (it is the prototype for interface dermatitis)
- the reaction results in pointed epidermal rete ridges at the junction, causing a characteristic "saw-tooth" appearance at the junction
- (if it affects the mucosa, the lesions are white instead of violaceous)
- Wickham striae are the white dots/lines that are classically seen with the lesions

14

What should we suspect in a patient presenting with dermatitis, dementia, and diarrhea?

- pellagra
- this is due to a deficiency in niacin (vitamin B3)

15

The classic salmon plaque-like lesions of psoriasis are found in the chronic form of the disease - what can trigger an acute onset of psoriasis?

- acute psoriasis (gottate) classically follows an infection with Streptococci

16

Explain the major developments occurring in eczematous, interface, psoriasiform, and blistering dermatoses. What are examples of each?

- eczematous: spongiosis; atopic eczema, allergic contact dermatitis
- interface: infiltrate at the DE junction, keratocyte apoptosis; lichen planus
- psoriasiform: ancanthosis, hyperkeratosis, parakeratosis, papillomatosis; psoriasis, lichen simplex chronicus
- blistering: acantholysis, vessicles/bullae; pemphigus, dermatitis herpetiformis