Chapter 25: Skin - Dermatoses, Blistering , Epidermal Appendage, and Infections Flashcards
Ichthyosis is a group of inherited disorders that results in what?
- Chronic, excessive keratin buildup (hyperkeratosis) –> fishlike scales
- Defective desquamation
All forms of ichthyosis exhibit a buildup of what; morphologic appearance?
Buildup of compated stratum corneum that is assoc. w/ loss of normal basket-weave pattern
Angioedema is closely related to urticaria and is characterized by what?
Edema of the deeper dermis and SQ fat
What are the histologic changes seen in Urticaria?
- Sparse superficial perivenular infiltrate consisting of mononuclear cells
- Collagen bundles are more widely spaced than in normal skin –> clear spaces in between
Urticaria (hives) is a common disorder of the skin characterized by what?
- Localized mast cell degranulation —> dermal microvascular hyperpermeability
- Results in pruritic edematous plaques (wheals)
Acute eczematous dermatitis is which type of hypersensitivity?
T-cell mediated inflammatory rxn (type IV hypersensitivity)
All types of eczematous dermatitis are characterized by what type of lesions and what occurs if persistent?
- Red, papulovesicular, oozing, and crusted lesions
- If persistent –> develop reactive acanthosis and hyperkeratosis that produce red scaling plaques
Which edematous finding characterizes acute eczematous dermatitis; how does this differ from urticaria?
- Spongiosa: edema seeps into the intercellular spaces of the epidermis, splaying apart keratinocytes, particularly in stratum spinosum
- In urticaria the edema is restricted to superficial dermis
In acute eczematous dermatitis, mechanical shearing of intercellular attachment sites (desmosomes) and cell membranes by progressive accumulation of intercellular fluid may result in formation of what?
Intraepidermal vesicles
Erythema multiforme is characterized by keratinocyte injury mediated by what?
Skin-homing CD8+ cytotoxic T cells
Which severe febrile form of erythema multiforme is often seen in children with lesions involving not only the skin but also the lips and oral mucosa, conjunctiva, uretha, and genital/perianal areas?
Stevens-Johnson Syndrome
Which life threatening complication may arise from Steven-Johnson syndrome?
Life-threatening sepsis as a result of 2’ infection due to loss of skin integrity
“Targetoid” lesions are characteristic of what?
Erythema Multiforme
What is interface dermatitis as it relates to erythema multiforme?
Lymphocyte infiltration along dermoepidermal jct, asooc. with degenerating and necrotic keratinocytes
Psoriasis is strongly linked to which HLA gene locus?
HLA-C; paricularly HLA-Cw*0602
What is the Koebner phenomenon and what 2 chronic inflammatory dermatoses can it be seen in?
- Induction of lesions in susceptible pt’s by local trauma, starts a self-perpetuating local inflammatory response
- Seen with Psoriasis and Lichen Planus
Which body regions most often affected in Psoriasis; how do they lesions appear?
- Skin of elbows, knees, scalp, lumbosacral areas, intergluteal cleft, and glans penis
- Well-demarcated, pink to salmon-colored plaque covered by loosely adherent silver-white scale
What are the nail changes seen in some pt’s with Psoriasis?
Yellow-brown discoloration (oil-slick), with pitting, dimpling, separation of the nail plate from underying bed (onycholysis), thickening, and crumbling
What is the characteristic histologic picture of established lesions seen with Psoriasis?
- Marked epidermal thickening (acanthosis)
- Downward elongation of the rete ridges –> “test tubes in a rack”
- Abundant mitotic figures
- Stratum granulosum is thinned or absent, and extensive overlying parakeratotic scale seen
Dilated, tortuous blood vessels within dermal papillae of Psoriasis lesions leads to what characteristic sign when scales are lifted from a plaque?
Auspitz sign: mult, minute, bleeding points when scale lifted from plaque
Which immune cells form aggregates within spongiotic foci of the superficial epidermis (spongiform pustules) and within the parakeratotic stratum corneum (munro microabscesses) in psoriasis?
Neutrophils (PMNs)
Which chronic inflammatory dermatitis classically involves regions with a high density of sebaceous glands such as the scalp, forehead (especially the glabella), external auditory canal, retroauricular area, nasolabial folds, and presternal area?
Seborrheic Dermatitis
What is the most common clinical expression of Seborrheic Dermatitis of the scalp?
Dandruff
What are the “Six P’s” of lichen planus?
Pruritic, Purple, Polygonal, Planar, Papules, and Plaques
Which chronic inflammatory dermatosis is a self-imited disorder of skin and mucosa, resolving spontaneously in 1-2 years?
Lichen Planus
Which complication may arise as a result of the chronic mucosal and paramucosal lesions associated with lichen planus?
SCC
What is the morphology of the cutaneous lesions of lichen planus and what is a hallmark finding?
- Itchy, violaceous, flat-topped papules that coalesce to form plaques
- Papules often highlighted by white dots/lines called Wickham striae, created by areas of hypergranulosis; appear lace-like
Oral lesions associated with lichen planus appear how?
White, reticulated, or net-like areas (lace like)
What is the characteristic appearance of the destructive lymphocytic infiltrate at the dermoepidermal interface in lichen planus?
Angulated zig-zag contour = “Saw-toothing”
What are the colloid or Civatte bodies seen in lichen planus and other chronic dermatoses in which basal keratinocytes are destroyed?
Anucleate, necrotic basal cells incorporated into inflammed papillary dermis
The lesions of lichen planus bear similarities to erythema multiforme, but differ in what regard?
- Changes of chronicity –> epidermal hyperplasia (acanthosis) +
- Thickening of the granular cell layer (hypergranulosis) +
- Stratum corneum (hyperkeratosis)
Pemphigus is caused by what?
IgG autoantibodies against desmogleins 1 and 3
Which type of pemphigus is characterized by large moist verrucous (wart-like) vegetating plaques studded with pustules found in the groin, axilla and flexural surfaces?
Pemphigus vegetans
Paraneoplastic pemphigus is most commonly associated with what malignancy?
non-Hodgkin lymphoma
What is the most common histologic denominator in all forms of pemphigus?
Acantholysis, the dissolution or lysis of the intercellular bridges that connect squamous epithelial cells
An immediately supra-basal acantholytic blister with single layer of intact basal cells resembling a “row of tombstones” is characteristic of which type of pemphigus?
Pemphigus vulgaris
What is a more benign form of pemphigus that is endemic Brazil and has a predilection for the scalp, face, chest, and back?
Pemphigus foliaceus
Epidermal, acantholytic blisters vs. subepidermal, non-acantholytic blisters describe which disorders?
- Epidermal, acanthylotic blisters = Pemphigus
- Subepidermal, non-acantholytic blisters = Bullous pemphigoid
Who is most often affected by Bullous Pemphigoid; where do these blisters predominantly occur?
- Elderly
- Inner thighs + flexor surfaces of forearms + axilla + groin and lower abdomen
How does the antibody deposition associated with Bullous Pemphigoid appear with direct immunofluorescence staining?
Linear deposition along dermoepidermal jct.
In Bullous Pemphigoid autoantibodies bind BPAG2, which is a component of what?
Hemidesmosomes
Which age group and sex is predominantly affected by dermatitis herpetiformis?
Males, most often in 3rd and 4th decades
Dermatitis herpetiformis is sometimes associated with what GI disease and how can it be treated?
Celiac disease; responds to gluten-free diet
What is the pathogenesis of dermatitis herpertiformis in pt with Celiac disease?
Develop IgA antibodies to gluten; cross-react with reticulin (component of anchoring fibrils of epidermal BM) –> subepidermal blister
Describe the lesions of dermatitis herpetiformis and where they are most often seen?
- Bilateral, symmetric and grouped
- Involving the extensor surfaces, elbows, knees, upper back, and buttocks
How can immunofluorescence staining help distinguish dermatitis herpetiformis?
Shows discontinous, granular deposits of IgA localizing to tips of dermal papillae
Epidermolysis Bullosa are a group of disorders causes by inherited defects in what; leads to what type of lesions and seen at what age?
Defects in structural proteins –> blisters at sites of pressure, rubbing or trauma at (or soon after) birth
The simplex type (most common) of epidermolysis bullosa results from mutations in what?
Genes encoding keratin 14 or keratin 5
Where is the blistering seen in the junctional type of epidermolysis bullosa?
Subepidermal blister at the level of the lamina lucida** in otherwise histologically **normal skin
Most cases of the junctional type of epidermolysis bullosa are due to what defects?
Autosomal recessive** defects in a subunit of **laminin
Urticaria and subepidermal vesicles assoc. w/ scarring exacerbated by exposure to sunlight is a feature of what?
Porphyrias
What are the 4 stages seen with Rosacea?
- Flushing
- Persistent erythema and telangiectasia
- Pustules and papules
- Rhinophyma: permanent thickening of nasal skin
Pt’s with rosacea have high cutaneous levels of what; how does this play a role in the pathogenesis?
Cathelicidin = important mediator of cutaneous innate immune response
Panniculitis refers to inflammation of what; what are the 2 distinct forms?
- Inflammation of subQ adipose tissue; preferentially affecting (1) lobules of fat, or (2) the CT separating fat into lobules
- 2 distinct forms: erythema nodosum and erythema induratum
Describe the presentation and course of the lesions associated with erythema nodosum?
- Erythematous plaques and nodules, more readily palpated than seen
- Over weeks, lesions usually flatten and become bruise-like, no residual scars
Occurrence of erythema nodosum is associated with what?
- Infections: β-hemolytic strep; tuberculosis
- Drugs: sulfonamides, OCP’s
- SARCOIDOSIS; IBD; certain malignant neoplasms
Which type of hypersensitivity is erythema nodosum?
Delayed-type (Type IV)
Histologic diagnosis of erythma nodosum requires what?
Biopsy of deep wedge of tissue to generously sample the subcutis
What is the distinct histopathology of the early and late lesions seen with erythema nodosum?
- Early: CT septae = widened by edema, fibrin exudation, and neutrophil infiltration
- Late: infiltration by lymphocytes, histiocytes, multinucleated giant cells —> septal fibrosis
Necrotizing vasculitis of sm-medium arteries and veins in deep dermis and subcutis + granulomatous inflammation w/ zones of caseous necrosis involving the fat lobule is associated with what?
Erythema induratum
What is the most common type of wart (verruca) and where does it occur on body and how do they appear grossly?
- Verruca vulgaris; frequently the hands (dorsum) and periungual areas
- Appear as gray-white to tan, flat to convex, small papules w/ rough, pebble-like surface
How can molluscum contagiosum be diagnosed clinically?
Umbilicated area –> curd-like material onto slide and stain with giemsa showing diagnostic molluscum bodies
Impetigo is most often caused by what?
S. aureus
Pathogenesis of impetigo leading to blister formation is a from a bacterial toxin causing what?
Cleavage of desmoglein 1, protein responsible for cell-cell adhesion within uppermost epidermal layers
Fungal hyphae of dermatophytes causing tinea can be stained with what and will appear how?
Stained with PAS —> bright pink to red hyphae within stratum corneum
