Path: Skin Pathology 3

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Unit 2, Week 2

Ichthyosis (4)

Genetically inherited: become apparant around time of birth
Acquired: Ichthyosis vulgaris,
Chronic excessive keratin buildup (hyperkeratosis)
Fish-scales

Ichthyosis: Morphology (2)

Buildup of compacted stratum corneum, loss of normal basket-weave pattern
Little to no inflammation

Ichthyosis: Pathogenesis

Defective desquamation, leads to retention of abnormally formed scale

Acute Inflammatory Diseases

Typically last days-weeks
Characterized by inflammatory infiltrate, edema, variable degrees of epidermal, vascular, or subcutaneous injury
Urticaria, Acute eczematous dermatitis, erythema multiforme

Urticaria

Localized mast cell degranulation, results in dermal microvascular hyperpermeability
Gives rise to wheals (pruritic edematous plaques)
Occurs most often between 20-40yo
Lesions develop and fade within hours, episodes may last for days or persist for months
Lesions: small, pruritic plaques to large edematous plaques
Persistent episodes may herald an underlying disease (collagen vascular disease)
Common sites: those exposed to pressure

Urticaria: Morphology

Perivenular infiltrate: mononuclear cells, eosinophils
Collagen bundles more widely spaced than in normal skin, result of superficial dermal edema
Dilated superficial lymphatic channels

Urticaria: Pathogenesis (3)

IgE-dependent response: most cases, follows exposure to many different Ags (food, pollens, drugs, insect venom)
IgE-independent response: various substrates directly degranulate mast cells, opiates, certain antibiotics, and radiographic contrast media
-also, exposure to chemicals (like aspirin) that suppress prostaglandin synthesis from arachidonic acid
Complement-mediated urticaria: seen in hereditary angioneurotic edema; inherited deficiency of C1 inbitor - unregulated activation of early componentsof complement system and production of vasoactive mediators

Acute Eczematous Dermatitis (4-5)

Chacterized by red, papulovesicular, oozing, crusted lesions that can develop into raised, scaling plaques due to reactive acanthosis and hyperkeratosis (prolonged disease)
Reaction pattern, NOT a disease
Categories:
-allergic contact dermatitis
-atopic dermatitis
-drug-related eczematous dermatitis
-photoeczematous dermatitis
-primary irritant dermatitis
Lesions vulnerable to bacterial superinfection

Acute Eczematous Dermatitis: Morphology (3)

Spongiosis:
-edema seeps into epidermis and separates keratinocytes
-accumulation can result in intraepidermal vesicles
Early stages:
-superficial and perivascular infiltrates composed of lymphocytes
-papillary epidermal edema
Mechanical shearing of desmosomes and cell membranes

Acute Eczematous Dermatitis: Pathogenesis (2)

Langerhans cells pick up Ags, travel to lymph nodes, and present Ags to naive CD4+ T cells
On Ag re-exposure, mem T cells extravasate into tissues and release cytokines and chemokines that recruit numerous inflam cells characteristic of eczema

Erythema Multiforme (2-4, 4)

Hypersensitivity reactions to certain infections and drugs
Acute and self-limited mucocutaneous disorder that is often mild
Affects all ages
Associated with:
-infections like herpes simplex, mycoplasmal infections, histoplasmosis, typhoid
-administration of certain drugs
-malignant disease
-collagen vascular diseases
Multiform lesions: macules, papules, vesicles, and bullae, characteristic target lesion
-lesions widely distributed but usually symmetric
Symmetric involvement of limbs
Stevens-Johnson syndrome - extensive and symptomatic febrile form of disease; involve lips and oral mucosa, conjunctiva, urethra, genital, and perianal areas; secondary infection: may result in sepsis, life-threatening
Toxic epidermal necrolysis: most severe rxn with widespread sloughing of epidermal surface; diffuse necrosis and sloughing of cutaneous and mucosal surfaces, infection and fluid loss

Erythema Multiforme: Morphology

Superficial perivascular lymphocytic infiltrate
Interface dermatitis: necrotic keratinocytes + lymphocytes along dermoepidermal junction
Later lesions:
-migration of lymphocytes into epidermis
-zones of epidermal necrosis with blister formation
-erosions due to epidermal sloughing

Erythema Multiforme: Pathogenesis

Epithelial cells destroyed by CD8+ cells

Chronic Inflammatory Dermatoses

Last for months to years
Scale formation, roughened appearance
Psoriasis
Seborrheic dermatitis
Lichen planus

Psoriasis (7)

All ages affected
Well-demarcated, pinkish plaque covered by loosely adherent silver-white scale
One cause of erythroderma = total body erythema and scaling
Nail pitting, yellow-brown discoloration, and onycholysis in 30% cases
May be associated with arthritis, myopathy, enteropathy, spondylitic joint disease, AIDS
Affects: elbows, knees, scalp, lumbosacral area, intergluteal cleft, glans penis
Pustular psoriasis
-rare variant
-multiple pustules arising on erythematous plaques
-may be benign and localized
-it can also be generalized andl ife threatening
Koebner phenomenon: local trauma can induce lesions in these patients

Psoriasis: Morphology (4)

Acanthosis (epidermal thickening)
Downward elongation of rete ridges
Stratum granulosum is thinned or absent, extensive overlying parakeratotic scale is present
Spongiform pustules: aggretates of neutrophils in spongiotic foci of superficial epidermis
Munro microabscesses: aggregates of neutrophils within the paraakeratotic stratum corneum
Thinning of epidermal layer overlying tips of dermal papillae containing dilated and tortuous BVs: multiple bleeding points when scale removed*

Psoriasis: Pathogenesis

Multifactorial with contributions from genetics as well as environment
Strong association between psoriasis and HLA-C
Accumulation of sensitized pop'ns of CD4+ TH1 and TH17 cells plus CD8+ effector
Cellular interaction ==> cytokines
TNF appears to be vital

Seborrheic Dermatitis (4)

Even more common than psoriasis
Involves regions with high density of sebaceous glands (scalp, forehead, external auditory canal, retroauricular area, nasolabial folds, presternal area
Lesions: macules and papules on red-yellow often greasy base, assoc with extensive scaling and crusting
Dandruff is common clinical expression in scalp
-seen as cradle cap in infants
HIV+ with low CD4 can develop severe form of seborrheic dermatitis

Seborrheic Dermatitis: Morphology

Mounds of parakeratosis containing neutrophils and serum at ostia of hair follicles

Seborrheic Dermatitis: Pathogenesis

....?

Lichen planus (8)

Pruritic, purple, polygonal, planar papules, plaques
Self-limited and most commonly resolves spontaneous 1 or 2 years after onset, leaves zones of postinflammatory hyperpigmentation
Oral lesions may persist for years
SCC can occur, but not directly related
Itchy, violaceous, flat-topped papules
Wickham striae: white dots or lines created by hypergranulosis
Lesions are symmetrically distributed on wrists, elbows, and glans penis
70% cases, oral lesions are white, reticulated, or netlike areas involving mucosa
Koebner phenomenon

Lichen planus: Morphology (4)

Interface dermatitis: infiltration of lymphocytes along dermoepidermal jxn
Anucleate, necrotic basal cells in papillary dermis = colloid/Civatte bodies
Zigzag contour of dermoepidermal interface
Lichen planopilaris: affects epithelium of hair follicles
Epidermal hyperplasia
Hypergranulosis
Hyperkeratosis
Hyperplasia of Langerhans cells are characteristic features of this disorder

Blistering Diseases (10)

Blisters are primary features
Can occur at different skin levels
Subcorneal: s corneum forms roof
Suprabasal: portion of epidermis + s corneum forms roof
Subepidermal: entire epidermis separates from dermis
Desmogleins (Dsg) 1 and 3 are components of desmosomes
Pemphigus vulgaris: targets Dsg1&3, blisters in deep suprabasal epidermis
Pemphigus foliaceus: targets Dsg1, superficial, subcorneal blisters
Bullous pemphigoid: targets fibrils that anchor hemidesmosomes
Epidermolysis bullosa: due to genetic defects in genes that code for proteins that form or stabilize desmosomes or hemidesmosomes

Pemphigus (3-5)

Inflammatory blistering disorders
Caused by autoAbs that result in dissolution of intercellular attachments within epidermis and mucosal epithelium
Variants:
-pemphigus vulgaris*
-pemphigus vegetans
-pemphigus foliaceus
-pemphigus erythematosus
-paraneoplastic pemphigus

Pemphigus vulgaris (3)

Most common type (>80% cases)
Involves mucosa and skin, esp scalp, face, axilla, groin, trunk, points of pressure
Primary lesions are superficial vesicles and bullae that rupture easily, leaving shallow erosions covered with dried serum and crust
Nikolsky's signs: lateral pressure on skin that is adjacent to blister causes epidermal detachment
Without treatment, fatal; even with treatment it's a serious disorder

Pemphigus vegetans

Rare form that usually presents not with blisters but with large, moist, verrucous (wart-like), vegetating plaques studded with pustules on groin, axillae, flexural surfaces

Pemphigus foliaceus (3)

More benign form that is endemic in Brazil
Scalp, face, chest, and back, and mucous membranes rarely affected
Bullae are so superficial that only zones of erythema and crusting, sites of previous blister rupture resulting in superficial erosions, are present on physical examination
Mucous membranes rarely affected
Much more benign than p. vulgaris

Pemphigus erythematosus

Localized, less severe form of pemphigus foliaceus, may selectively involve malar area of face in lupus erythematosus-like fashion

Paraneoplastic pemphigus

Occurs in association with various malignancies, most commonly non-Hodgkin lymphoma

Pemphigus: Morphology

Acantholysis
Suprabasal acantholytic blister leaves intact layer of basal cells, 'tombstoning' - pemphigus vulgaris
P. foliaceus: blister selectively involves epidermis at s. granulosum
Infiltration of superficial dermis by lymphocytes, histiocytes, and eosinophils

Pemphigus: Pathogenesis (3)

Caused by IgG autoAbs against desmogleins, show linkage to specific HLA types
Net-like pattern of intercellular IgG deposits
Abs disrupt intercellular adhesive function

Bullous Pemphigoid (3)

Autoimmune, results in chronic, pruritic bullous eruptions
Generally affects elderly*
May involve only the skin, locally or generally, or skin and mucosal surfaces
Lesions: tense bullae, filled with clear fluid, on normal or erythematous skin
Do not rupture easily, and (without infection) heal without scarring
Sites of involvement: inner thighs, flexor surfaces of forearms, axillae, groin, lower abdomen

Bullous Pemphigoid: Morphology

Subepidermal, nonacantholytic blisters
Superficial and possibly deep inflammatory infiltrate
Eosinophils with degranulation seen beneath basal layer
Vacuolated basal cell layer

Bullous Pemphigoid: Pathogenesis

Linear deposits of Ig and complement in basement membrane
-subsequent injury results from neutrophil and eosinophil recruitment
Reactivity involving hemidesmosomes (where most of BPAG is)

Dermatitis Herpetiformis (4)

Rare autoimmune disorder characterized by urticaria and grouped vesicles
Herpetiformis = clustered appearance of lesions
Sometimes occurs in association with intestinal celiac disease and responds to gluten-free diet
Urticarial plaques and vesicles are extremely pruritic
Lesions are bilateral, symmetric, grouped, involving preferentially extensor surfaces

Dermatitis Herpetiformis: Pathogenesis

IgA Abs to dietary gluten cross-react with reticulin, component of anchoring fibrils that tether epidermal basement membrane to superficial dermis, resultant injury and inflammation produce a subepidermal blister
-assoc. with celiac disease

Dermatitis Herpetiformis: Morphology

Fibrin and neutrophils accumulate selectively at tips of dermal papillae (form microabscesses)
Subepidermal blisters
Granular deposits of IgA
-seen by direct immunofluorescense
-localized to tips of dermal papillae

Epidermolysis Bullosa (4)

Epidermolysis bullosa: constitutes group of disorders caused by inherited defects in structural proteins that lend mechanical stability to skin
Proclivity to form blisters at sites of pressure, rubbing, or trauma, at or soon after birth
~10 genes encode structural proteins at dermoepidermal junction
In simplex type: defects of basal cell layer of epidermis result from mutations in genes encoding keratins 5 or 14
In junctional type: blisters occur in otherwise histologically normal skin at level of lamina lucida
In dystrophic types: blisters develop beneath lamina densa, in association with rudimentary or defective anchoring fibrils

Porphyria

Disoders of porphyrin metabolism
Porphyrins normal constituents of hemoglobin, myoglobin, cytochromes

Acne Vulgaris (5)

Affects both males and females, more severe in males
Usually milder in Asians
Open comedones: small follicular papules containing a central black keratin plug
-color due to oxidation of melanin pigment (not dirt)
Closed comedones: follicular papules without a visible central plug (trapped beneath surface), potential sources of follicular rupture and inflammation
Inflammatory acne is characterized by erythematous papules, nodules, and pustules
Acne conglobata: most severe form, with sinus tract formation and scarring

Acne Vulgaris: Morphology (4) [FIX]

Changes in keratinization of lower portion of follicular infundibulum with development of a keratin plug blocking outflow of sebum to skin surface
Hypertrophy of sebaceous glands with puberty or increased activity due hormonal stimulation
Lipase-synthesizing bacteria colonizing upper and midportion of hair follicle, converting lipids within sebum to pro-inflammatory FAs
Inflammation of follicle associated with release of cytotoxic and chemotactic factors

Acne Vulgaris: Pathogenesis

4 Factors:
-follicular hyperkeratinization
-increased sebum production
-propionibacterium acnes within follicle
-inflammation
......?? [fill in]

Rosacea (2-4)

Predilection for females
Four stages
-flushing episodes (pre-rosacea)
-persistent erythema and telangiectasia
-pustules and papules
-rhinophyma: permanent thickening of the nasal skin by confluent erythematous papules and follicular prominance
Characterized by: facial flushing, telangiectasis, erythema, papules, pustules

Rosacea: Morphology

Perifollicular infiltrate composed of lymphocytes surrounded by dermal edema
Pustular phase: neutrophils may occupy follicles-follicular rupture may cause granulomatous dermal reaction
Rhinphyma

Rosacea: Pathogenesis

----?

Panniculitis

Inflam rxn of subcutaneous adipose tissue
Affects CT septa or fat lobules
Often involves lower legs
Types:
-erythema nodosum
-erythema induratum
-Weber-Christian disease
-factitial panniculitus
-type assoc. with lupus

Erythema Nodosum

Most common form panniculitis
Assoc ......[FILL IN]

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