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Diseases of the Epidermis
  1. Ichthyoses
  2. Darrier Disease
  3. Psoriasis
  4. Pemphigus Vulgaris
Ichthyoses
  • "Fish Skin"
  • Disease of the epidermis - epidermal thickening and scales
  • inherited - overproduction of keratin, decreased keratin desquamation → thickening of keratin layer (hyperkeratosis)
  • defect unk? - perhaps increased cohesiveness of stratum corneum cells
  • microscopic: thick stratum corneum, thin epidermis
Darrier Disease (Keratosis Follicularis)
  • Disease of the epidermis
  • Inherited autosomal dominant
  • defect: intercellular matrix; mutation in ATP2A2 gene on chromo 12
  • Lesions: tan papules 2-4mm; warty elevations on forehead, ears, back, scalp, chest
  • microscope: papule shows suprabasilar cleft; roof of cleft is cone of compact keratotic material (keratotic plugging)
Psoriasis (general description)
  • Disease of the epidermis
  • common chronic inflammatory dermatoses; 1-2% of US pop affected
  • any age; MC onset late 20's
  • sometimes assoc with arthritis, myopathy, enteropathy, AIDS
Psoriasis (sites)
  • elbows
  • knees
  • scalp
  • lumbosacral areas
  • intergluteal cleft
  • glans penis
Psoriasis (Macroscopic appearance)
  • well demarcated, pink plaques covered by silvery scales
  • may be total body erythema & scaling: "erythroderma"
  • nail changes: pitting, thickening, onycholysis (separation from nail bed)
  • rare: small pustules form on plaques: pustular psoriasis
Psoriasis (Microscopic appearance)
  • acanthosis (thickening of squamous epi) with elongated rete ridges
  • parakeratosis (nuclei in keratin layer) and absence of granular cell layer
  • mitoses above basal layer
  • Munro abscesses (collections of neutrophils) within superficial epithelium
  • Dilated BVs in dermis clinical erythema
Psoriasis (cause)
  • unk/multifactorial?
  • hypothesis:
  1. genetic (1/3 have family hx
  2. assoc with certain HLA types
  3. trauma - lesions at site = Koebner phenomenon
  4. Immune basis: activated T cells present, psoriasis responds to immunosuppressants (cyclosporine)
Pemphigus Vulgarus PV (general description)
  • Disease of the epidermis
  • Chronic blistering skin disorder
  • AI; IgG Ab reacts with epidermal Ag → diminished cohesiveness of epidermal keratinocytes - blister formation
  • all age groups, MC 40-60yoa
  • blister d/t ↓cohesiveness of epidermal keratinocytes!
Pemphigus Vulgarus (Pathology)
  • Separation of outer epidermal layers from basal layers - suprabasalar blisters
  • blisters: contain lymphocytes, mΦ, eosinophils, neutrophils (esp in perivascular areas)
  • Direct IF of perilesional skin: intercellular deposits of IgG and C!
  • biopsy: take part of the edge of blister!
Pemphigus Vulgarus (Clinical features)
  • lesions on scalp, mucous membrane, periumbilical area
  • blisters large and rupture easily
  • PV may be assoc with other AI disorders: MG, SLE
Diseases of the Basement Membrane
  • Epidermolysis Bullosa
  • Bullous Pemphigoid
  • Dermatitis Herpetiformis
  • Erythema Multiforme
  • Systemic Lupus Erythematosus
  • Lichen Planus
Epidermolysis Bullosa
  • Formation of blister in the BMZ at sites of trauma
  • blisters start at birth or soon after
  • classified based on site:
  1. Epirdermolytic EB
  2. Junctional EB
  3. Dermolytic EB
Epidermolytic EB
  • Type of Epidermolysis Bullosa
  • transmitted as Autosomal Dominant
  • Cytolysis of basal keratinocytes
  • blisters heal by scarring
Junctional EB
  • Type of Epidermolysis Bullosa
  • transmitted as Autosomal Recessive
  • blisters in lamina lucida
  • can be benign or severe/fatal within first 2 years
Dermolytic EB
  • type of Epidermolysis bullosa
  • Autosomal Dominant or Recessive
  • blisters beneath lamina densa
  • blisters heal; leave atrophic scarring
Bullous Pemphigoid
  • Disease of Basement Membrane
  • common AI blistering disorder
  • old people
  • Lg (4-8cm), tense subepithelial bullae in skin and mucosa; painful
  • result from detachment of epithelium from underlying CT; d/t immunoogically mediated damage to BM
Bullous Pemphigoid (sites)
  • Inner thigh
  • flexor surfaces of forearms
  • axilla
  • groin
  • lower abdomen
Bullous Pemphigoid ( Microscopic appearance)
  • subepidermal nonacantholytic blister (no thickening)
  • perivascular infiltrate of lymphocytes, eosinophils
  • bullae contain eosinophils, lymphocytes, neutrophils, fibrin
  • IF test: linear BMZ deposits of IgG + C
Dermatitis Herpetiformis (general info)
  • rare, chronic, recurrent, pruritic
  • age of onset: 3rd and 4th decades
  • M>F
  • associated with gluten sensitivity
Dermatitis Herpetiformis (sites)
  • extensor surfaces: elbows, knees, upper back, buttocks
  • billaterally and symmetrically
  • oral mucosa not affected
Dermatitis Herpetiformis (Macroscopic appearance)
  • Vesicles grouped like true herpesvirus infection
  • subepidermal
Dermatitis Herpetiformis (Microscopic appearance)
  • neutrophils, eosinophils, fibrin at tips of dermal papillae (microabscesses)
  • overlying basal cell vacuolization → microscopic blisters coalesce = Lg subepidermal blisters
  • IF test shows granular deposits of IgA at tips of dermal papillae!
  • may be assoc with celiac, respond to gluten free
  • HAL-B8, HLA-DR3 prone to this disease
Erythema Multiforme (general desc)
  • Acute, self-limited allergic dermatitis d/t drugs, infections, malignancy, collagen-vascular disease
  • believed to be CMI injury/dysfunction
Erythema Multiforme (clinical appearance)
  • Lesions widespread; present as macules, papules, vesicles, bullae
  • target lesion: (iris lesions) central dark red zone with a blister, surrounded by paler area
  • symmetric involvement of extremities
Erythema Multiforme (Stevens-Johnson Syndrome)
  • severe, febrile form of EM
  • MC in children
  • swelling, bleeding, serosanguinous crusting of lips and oral mucosa
  • conjunctiva, urethra, anogenital regions also affected
Erythema Multiforme (microscopic appearance)
  • keratinocyte degeneration & necrosis→vesiculation
  • dermis shows varying infiltration of lympho-histiocytes
  • target lesions = central necrosis surrounded by perivenular inflammation
Systemic Lupus Erythematosus (SLE) (general desc)
  • Chronic multisystem AI disease
  • involving skin, kidneys, joints, serosal mem, heart; assoc with autoantibodies
  • cutaneous involvement may be severe and disfiguring
  • 3 forms:
  1. Chronic Cutaneous (discoid) Erythematosus
  2. Subacute Cutaneous Erythematosus
  3. Acute SLE
Chronic Cutaneous (discoid) Erythematosus (general desc)
  • form of SLE
  • limited to skin on face, malar area, scalp, ears, neck
  • lesions start as slightly elevated papules w/rough scale of keratin
  • later assume disc shape w/hyperkeratotic margin & pale center
  • lesions form into disfiguring scars
Chronic Cutaneous (discoid) Erythematosus (microscopic appearance)
  • irreg proliferation & thinning of epithelium
  • edema at Derm-Epiderm jxtn
  • vacuolation of basal cells
  • patchy infiltrate of lymphocytes
  • thickening of BMZ
  • deposition of IgG + C along BMZ: pos lupus band test
  • ANA in <10%
Chronic Cutaneous (discoid) Erythematosus (immunopathogenesis)
  • humoral & CM mechanisms: destruction of pigment-containing basal cells
Subaccute Cutaneous Erythematosus
  • form of SLE
  • Skin, MSK, kidneys
  • Upper chest, upper back, extensor surfaces of arms
  • lesions: begin as erythematous papules → enlarge into annular lesions
  • no sig scarring
  • ANA elevated in 70%
Acute SLE
  • >80% pts with SLE have acute cutaneous manifestation
  • skin may precede systemic
  • Lesions: maculopap rash of chest & extremities
  • delicate erythema of malar area of face: butterfly rash; lasts a few hours/days
  • heal without scarring
  • ANA elevated in >90%
Lichen Planus (general)
  • Disease of Basement mem
  • common, chronic: skin & mucous mem; slef limiting
  • skin lesions resolve in 1-2 yrs, oral lesions persist several years
Lichen Planus (macroscopic appearance)
  • violaceous papules w/white dots/lines: wickham striae
  • mult lesions symmetric; freq on extremities, wrists, elbows
  • oral lesions present as white reticulated areas on mucosa (buccal, lateral part of dorsum)
  • cause unknown; CMI injury to basal cells?
Lichen Planus (microscopic appearance)
  • parakeratosis
  • saw-tooth pattern deep surface of epithelium
  • liquefaction degen at DE jxtn
  • anucleate, necrotic basal cells→ colloid or civatte bodies
  • dermis has dense band like infiltrate of PMN in upper dermis; T-cells may predominate
Inflammatory Diseases of the Superficial and deep Vascular bed
  • Urticaria, angiodema, hereditary angioneurotic edema
  • cutaneous necrotizing vasculitis
  • allergic contact dermatitis
  • granulomatous dermatitis
  • sarcoidosis
Urticaria
  • Inflamm of Superficial and deep vasc bed
  • common, rash, wheal formation resulting from focal mast cell degranulation→ ↑ cap perm w/release of plasma into skin and subQ
  • mainly in young adults
  • IgE mediated allergy; mast cell degen d/t chemicals, drugs, insect bites
  • Micro: scanty perivasc infiltrates of PMNS, no mast cell ↑
Angioedema (Giant Urticaria)
  • Inflamm disease of superficial & deep vascular bed
  • massive fluid escape into tissues from BV
  • large edematous swellings
  • in allergic: rxn to sensistizing substances incl food (eggs)
  • attacks may be without obvi cause
Hereditary angioneurotic edema
  • inflammatory disease of sup and deep vasc bed
  • Autosomal dominant
  • caused by mutation of C1-esterase inhibitor
  • involves GIT and larynx: laryngeal edema can be fatal
Cutaneous Necrotizing Vasculitis (general description)
  • inflamm disease of superficial and deep vasc bed
  • aka allergic cutaneous vasculitis
  • immune complex deposition in vascular walls at injury site or where venous flow is slowed
  • neutrophils attracted to site; release lusomal enzymes and damage endothelium→ fibrin deposition
  • assoc with HBV, HCV, RA, SLE, UC, lymphoma
Cutaneous Necrotizing Vasculitis (microscopic appearance)
  • neutrophilic infiltration of vessel wall
  • Fibrin deposition
  • extravasation of RBC's
Cutaneous Necrotizing Vasculitis (clinical appearance)
  • multiple purpuric papules 2-4mm
  • on lower extremities or at sites of pressure
  • sm BV's in joints, GIT, kidney may be involved
Allergic contact dermatitis
  • inflammatory disease of superficial and deep vascular bed
  • Cell mediated hypersens to exogenous sensitizing agents (poison ivy, oak)
  • path: separation of epidermal keratinocytes by edema fluid→ spongiosis
  • Clinical appearance: marked itching/burning; Hx of previous exposure
Granulomatous Dermatitis
  • Inflamm disease of superficial & deep vasc bed
  • in response to indigestible Ag implanted accidentally into skin (silicon breast implant)
  • usually unknown cause
  • path: formation of granulomas
Sarcoidosis
  • Inflamm disease of superficial & deep vasc bed
  • granulomatous; cause unknown
  • lungs, skin, LN's, spleen involved
  • epithelioid granulomas with no central necrosis
  • skin lesions: papuiles, plaques, nodules in dermis & subcutis
Scleroderma
  • Disorder of Dermal CT
  • kidneys, lungs, heart, esoph & SI also involved
  • lesions in dermis
Scleroderma: lesions
  • large collagen bundles parallel to epidermis: hypocellular!
  • patchy lympho & plasma cell infiltration
  • sweat glands & hair follicles obliterated
  • late stage: subQ fat replaced by collagen
Scleroderma: clinical features
  • 30-50yoa; F:M = 4:1
  • non pitting edema: hands/fingers/extremities
  • affeted areas are hard & tense; face is mask like and expressionless
  • late stage: skin over body is thick, dense, fibrotic, fixed to underlying tissue
Inflammatory disorders of the Panniculus
  • Erythema Nodosum
  • Erythema Induratum
  • Panniculus = subQ fatty tissue
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