Skin I (a) Flashcards by Elyaa Saleh

Causes of Urticaria

Pollens, foods, drugs, and insect venom

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Epi of Urticaria

20-40 yrs of age

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Patho of Urticaria

Immediate (type 1) hypersensitivity reaction -> corss-linkage of IgE on mast cells which cause degranualtion

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Microscopic Findings:
* Superficial perivenular infiltrate of mononuclear cells (Lymphatic vessel dilatation)
* Superficial dermal oedema, creating more widely spaced collagen bundles
* Degranulation of mast cells,

features of?

Urticaria

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Degranulation of mast cells in Urticaria can highlighted using ——– stain

Giemsa stain

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CP of Urticaria

Erythematous, oedematous, and Pruritic wheals(form after the degranulation of mast cells)

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Tx of Urticaria

Antihistamines, systemic steroids

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pressure Urticaria are lesions found only in areas exposed to ——–?

pressure

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Heriditray Angioedema is caused by what type of deficiency?

C1 esterase inhibitor

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Hereditary Angioedema affects?

1) lips,
2) throat,
3) eyelids,
4) genitals, and
5) distal extremities

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CP of Acute Eczematous Dermatitis (Eczema)

Oozing/ crusted Red papules, often with overlying vesicles

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Causes of Acute Eczematous Dermatitis (Eczema)

1. Allergic Contact Dermatitis (most common): Topical exposure to allergen
2. Atopic Dermatitis: Allergen exposure or defects in keratinocyte barrier function
3.Drug-related Eczematous Dermatitis: Hypersensitivity reaction to a drug

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cause of Allergic Contact Dermatitis

Type IV hypersensitivity reaction secondary to contact allergens (e.g, poison ivy, nickel)

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patho of Allergic Contact Dermatitis

Contact of allergen (poisin ivy) w/ skin –>

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CP of allergic contact dermatitis

localized pruritic (itchy) skin lesions, blisters w/ clear fluid

* bullae: blisters w/ clear fluid

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Microscopic Findings:
* Spongiosis (epidermal odema)
* Intercellular bridges are stretched
* Superficial perivascular lymphocytic infiltrate
* Oedema of dermal papillae
* Mast cell degranulation

features of?

Allergic Contact Dermatitis

*note very similar micro features of Urticaria

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Cause of Erythema Multiforme

Hypersensitivity response to:
* Infections(Herpes Simplex Virus and Mycoplasma)
* Drugs (Sulfonamides, Penicillin, Salicylates, Hydantoins, Antimalarials)

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*pathophysio

In Erythema Multiforme Skin-homing Cytotoxic T-cells attack the ———- of the skin and the ————, which may display antigens that cross-react with the inciting drug or microbe

Basal cells, mucosa

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CP of Erythema Multiforme

Target- like papules
(consisting of red macules or papules with pale vesicular or eroded centers)

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Macroscopic features:
* pathces have pale, vesicular, or eroded centers (Target-like papules)

Microscopic Findings:
* Dermal oedema
* lesions w/ degenerating (apoptotic) keratinocytes w/ lymphocytic infiltrates

Erythema Multiforme

*keratinocytes: the major cell type of the epidermis

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2 severe forms of Erythema Multiforme

Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

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cause of Psoriasis

* chronic skin inflammatory disorder

Multifactorial immunologic disease, in which both genetic (e.g. Human Leukocyte Antigen [HLA] types) and environmental factors contribute to risk

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Patho of Psoriasis

Sensitised populations of T cells secrete cytokines and growth factors that induce keratinocyte hyper- proliferation

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CP of Psoriasis

pink to salmon-coloured palques w/ silvery scaling

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Microscopic Findings: * Epidermal thickening **(acanthosis), w/ parakeratotic (nuclei still in stratum corneum)** * **loss of the stratum granulosum** and parakeratotic scale (due to lack of maturation) * **Regular elongation of the rete ridges** * Thinning of the epidermal cell layer overlying the tips of dermal papillae Features of?

**Psoriasis**

patho of Linchen PLanus | * chronic inflammatory skin disorder

CD8+ T cell-mediated cytotoxic immune response against antigens in the **basal cell layer and the dermo-epidermal junction**

Epi of Lichen Planus

Uncommon disorder; Middle-aged adults

# ** CP of Lichen Planus

**6 P's** 1) **P**ruritic, **p**urple, **p**olygonal, **p**lanar **p**apules, and **p**laques of skin and squamous mucosa 2) Mucosal involvement --> **Wickham striae**

# ** Microscopic Findings: * The lymphocytes are intimately associated with **basal keratinocytes**, which often atrophy or become necrotic * **"zig-zag" contour/"saw-tooth" infiltrate of lymphocytes at Dermo-epidermal interface (junction)** * Presence of anucleate, necrotic basal cells (**colloid bodies or Civatte bodies)** features of?

Lichen Planus

cause of Lichen simplex Chronicus

**Response to local repetitive trauma**, such as continual rubbing or scratching

CP of Lichen Simplex Chronicus

Raised, erythematous, and scaly lesions

Microscopic Findings: * **Acanthosis** (epi thickening) * Hyperkeratosis * **Hypergranulosis** ( ↑ thickness of the **stratum granulosum)** * **Solar elastosis** * Elongation of the rete ridges * **Fibrosis of the papillary dermi**s * Dermal chronic inflammatory infiltrate features of?

Linchen Simplex Chronicus

cause of Impetigo | * superficial bacterial infection

Staphylococcus aureus, Streptococcus pyogenes

Epi of Impetigo

* Most common bacterial infections of the skin * Primarily in children

CP of Impetigo

lesions w/ Honey-coloured crusting

Microscopic Findings: * Accumulation of **neutrophils beneath the stratum corneum** that often produces a **sub-corneal pustule** * Superficial dermal inflammation accompany these findings * **Bacterial cocci** in the superficial epidermis (demonstrated by Gram stain) features of?

impetigo

obv+ skin condition

Skin condition: Superficial dermal fungal infection caused by **Candida albicans** Obv: Satelite lesions

Microscopic Findings: *Neutrophilic infiltrate in the epidermis ***Psoriasiform hyperplasia**

Candidiasis of the Skin | Psoriasiform hyperplasia-> Candida

Stain used for Candida causing superfical Dermal fungal infection

**PAS**

Obv+ skin disorder

Condition: Deep dermal fungal infection caused by **Apergillus** Obv: A- Erythematous subcutaneous nodule B- Focally haemorrhagic lesion

Deep Dermal fungal infection caused by Aspergillus is due to Tissue damage and often ----------------- Response

**granulomatous**

Histochemistry for Deep Dermal fungal infection caused by Aspergillus

1) PAS- Periodic Acid-Schiff 2) Gomori methenamine silver stains | *identify fungal organisms

cause of Verrucae (Warts) | * viral infection

Human Papilloma Virus (HPV)

patho of Verrucae (Wrats)

Viral E6 and E7 onco-proteins lead to dysregulated epidermal cell growth and increased survival

Microscopic Findings: * Epidermal hyperplasia * Cytoplasmic vacuolisation [koilocytosis] (preferentially of the more superficial epidermal layers) --> **Halos of pallor surrounding infected nuclei** * Infected cells with **prominent kerato-hyalin granules** and **jagged eosinophilic intracytoplasmic protein aggregates** (result of impaired maturation) features of?

Verrucae (Warts)

the 4 types of Verrucae (Wrats)

1. **Verruca Vulgaris** 2. Verruca Plana (Flat Wart) 3. Verruca Plantaris/Palmaris 4. Condyloma Acuminatum (Venereal Wart)

most common type of Verrucae (Wrats)

**Verruca Vulgaris**

loc of Verruca Vulgaris

dorsum of the hand

CP of Verruca Vulgaris

**Gray-white to tan**, flat to convex, 0.1-1 cm papule with a rough, **pebble-like surface**

Loc of Verruca Plana (Flat Wart)

face

CP of Verruca Plana (Flat Wart)

Flat, smooth, tan macules

Verucca Vulgaris presents w/ Rough, --------------to --------------- skin coloured papule/plaque Macroscopically

hyperkeratotic to papillomatous | Hyperkeratotic --> thickening of the outer layer of the skin

Macroscopic features: - Rough, **hyperkeratotic to papillomatous skin coloured papule/plaque** microscopic features : - Papillomatous hyperplasia - Prominent granular layer - **Inward bending of rete** - Koilocytosis features of ?

Veruuca Vulgaris

# ** what type of Verruca (Wrats) has the following microscopic features: - Multiple **“bird’s eye” nuclei** in the granular cell layer

**Verruca Plana**

loc of Verruca Plantaris/Palmaris

Soles and palms

CP of Verucca PLantaris/ Palmaris

Rough, scaly lesions

Loc of Condyloma Acumuinatum (Venereal Wrat)

Penis, female genitalia, and perianal areas

Macroscopic features: - Warty **cauliflower-like lesion** w/ papillary or polypoid fronds Microscopic features : - Papillomatous mammillated epithelial hyperplasia - Koilocytic changes - Hyperkeratosis features of?

Condyloma Acuminatum (Venereal Wart)

cause of Pemphigus

Autoimmune disorder

patho of Pemphigus

* **Antibody-mediated (type II) hypersensitivity reactions** * **IgG auto-antibodies** that bind to intercellular desmosomal proteins (Desmoglein types 1 and 3) of skin and mucous membranes

Epi of Pemphigus

Rare; Elderly women

Clinical presentation of Pemphigus

**Superficial flaccid vesicles and bullae that rupture easily**

Microscopic Findings: * **Acantholysis**: Lysis of the intercellular adhesive junctions between neighbouring squamous epithelial cells that results in the rounding up of detached cells * **Superficial dermal infiltrates comprised of lymphocytes, macrophages, and eosinophils** features of?

Pemphigus

Direct Immuno-Fluorescence of Pemphigus

Fishnet-like pattern of intercellular IgG deposits

* Acantholysis selectively involves the layer of cells immediately above the basal cell layer, giving rise to a supra-basal acantholytic blister what type of Pemphigus is this?

Pemphigus Vulgaris

# ** microscopic features; - **Acantholysis in the granular cell layer with “missing” stratum corneum** - Neutrophils in the granular cell layer - Separation of the corneum from the rest of the epidermis features of?

Pemphigus Foliaceus

Cause of Bullous Pemphigoid

Autoimmune disorder

Patho of Bullous Pemphigoid

* Antibody mediated **(type II)** hypersensitivity reactions * * Linear **deposition of IgG antibodies** and complement in the epidermal basement membrane

CP of Bullous Pemphigoid

**Multiple fluid filled blisters**

Microscopic Findings: * Perivascular infiltrate of lymphocytes and variable numbers of eosinophils, occasional neutrophils * Superficial dermal oedema * Associated basal cell layer vacuolisation; The vacuolated basal cell layer eventually gives rise to a **fluid-filled sub-epidermal non-acantholytic blister** features of?

Bullous Pemphigoid

Direct Immuno-Fluorescence of Bullous Pemphigoid

Linear deposition of IgG antibodies and complement in the epidermal basement membrane

cause of Dermatitis Herpetiformis

Autoimmune disorder

Epi of Dermatitis Herpetiformis

* Males * 80% occurs is **ass. w/ Coeliac disease**

patho of Dermatiis Herpetiformis

Genetically predisposed persons develop: *** IgA antibodies to dietary Gluten** (derived from the wheat protein Gliadin) and ***IgA auto-antibodies that cross-react with epidermal transglutaminase** , expressed by keratinocytes

# ** CP of Dermatitis Herpetiformis

Pruritic urticaria and **grouped vesicles**

# ** Microscopic Findings: * **Neutrophils accumulate selectively at the tips of dermal papillae**, forming small micro-abscesses- **"Papillary Abscess"** * The basal cells overlying these micro-abscesses show vacuolisation and focal **dermo-epidermal separation** that ultimately coalesce to form subepidermal blisters features of?

Dermatitis Herpetiformis

# ** Direct immunofluorescence of Dermatitis Herpetiformis

Discontinuous, **granular deposits of IgA localised in the tips of dermal papillae**