Dermatology
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2015-05-25 15:24
Histology
Epidermal layers and junctions:| Question | Answer |
|---|---|
| What are the layers of the epidermis, from top to bottom? | Stratum Corneum, Lucidum, Granulosum, Spinosum, Basale [California likes Girls in String Bikinis] |
| What is found in the Stratum Corneum? | Keratin |
| What cell junction is found in the Stratum Spinosum? | Desmosomes |
| What is found in the Stratum Basale? | Stem cells |
| What infection affects the Stratum Granulosum? | Staphylococcus Scalded Skin |
| Tight junctions are composed of [?] | Claudins and Occludins [aka Zonula occludens] |
| What do the tight junctions do? | Impermeable to water: prevent solute movement |
| Adherens junctions are composed of ? | CADherins (Ca++ Dependent ADhesion molecules) [Rhymes with Adherens] |
| What do adherens junctions do? | "Belt" connecting actin cytoskeletin of adjacent cells |
| Loss of [?] promotes metastasis | E-cadherin (Ex. Lobular carcinoma) |
| What do the desmosomes do? | Cell-Cell adhesion Structural support via keratin interactions |
| Desmosomes are made of [?] | Desmoglein |
| Desmosomes are targeted in what dermatologic disease? | Pemphigus Vulgaris: autoantibodies against Desmoglein [DAMN is a Vulgar word] |
| What do gap junctions do? | Allow electrical and chemical communication between cells |
| Gap junctions are made of [?] | Connexon channel proteins |
| What do hemidesmosomes do? | Connect keratin to basement membrane |
| Hemidesmosomes are made of [?] | Integrins: membrane proteins that bind to collagen and laminin in the basement membrane |
| Hemidesmosomes are targeted in what dermatologic disease? | Bullous Pemphigoid [Bullous is down bullow] |
Macroscopic terms
| Question | Answer | Column 3 |
|---|---|---|
| Macule | Flat lesion with well-circumscribed change in skin color < 5mm | Freckle, labial macule |
| Patch | Macule > 5mm | Large birthmark (congenital nevus) |
| Papule | Elevated solid skin lesion < 5mm | Mole (nevus), acne |
| Plaque | Papule > 5 | Psoriasis |
| Vesicle | Small fluid-containing blister < 5mm | Chickenpox, shingles |
| Bulla | Large fluid-containing blister > 5mm | Bullous pemphigoid |
| Pustule | Vesicle containing pus | Pustular psoriasis |
| Wheal | Transient smooth papule or plaque | Hives (urticaria) |
| Scale | Flaking off of stratum corneum | Eczema, psoriasis, SCC |
| Crust | Dry exudate | Impetigo |
Microscopic terms
| Question | Answer | Column 3 |
|---|---|---|
| Hyperkeratosis | ↑ thickness of stratum corneum | Psoriasis |
| Parakeratosis | Hyperkeratosis with retention of nuclei in stratum corneum | Psoriasis |
| Acantholysis | Separation of epidermal cells | Pemphigus vulgaris |
| Acanthosis | Epidermal hyperplasia (↑ spinosum) | Acanthosis nigricans |
| Dermatitis | Inflammation of the skin | Atopic dermatitis |
Skin disorders (Common, blistering)
| Question | Answer |
|---|---|
| Albinism | ↓ melanin production d/t ↓ tyrosinase activity (normal # of melanocytes) Neural crest cell fail to migrate during development |
| Melasma (chloasma) | Hyperpigmentation assoc w pregnancy or OCP use "mask of pregnancy" |
| Vitiligo | Irregular areas of complete depigmentation Caused by a ↓ in melanocytes |
| Verrucae | Warts - caused by HPV Epidermal hyperplasia, hyperkeratosis, koilocytosis Condyloma acuminatum on genitals |
| Melanocytic nevus | Common mole. Melanoma can arise from congenital or atypical moles Intradermal nevi are papular Junctional nevi are flat macules |
| Urticaria | Hives Pruritic wheals that form after mast cell degranulation |
| Ephelis | Freckle Normal number of melanocytes, ↑ melanin pigment |
| Atopic dermatitis (eczema) | Pruritic eruption, commonly on skin flexures Assoc with Asthma, Allergic rhinitis Starts on the face in infancy, later in Antecubital fossa |
| Allergic contact dermatitis | Type 4 hypersensitivity rxn (nickel, poison ivy, neomycin) |
| Psoriasis | Papules and plaques with silvery scaling, esp on knees and elbows Acanthosis with parakeratotic scaling (nuclei still in stratum corneum) ↑ stratum spinosum, ↓ stratum granulosum Auspitz sign - pinpoint bleeding spots when scales are scraped off Assoc w nail pitting and psoriatic arthritis Treat with Vitamin D analogs: Calcipotriene, Calcitriol, Tacalcitol |
| Seborrheic keratosis | Flat, greasy, pigmented squamous epithelial proliferation Keratin-filled cysts (horn cysts) Looks "stuck on" Lesions on head, trunk, extremities Common benign neoplasm of older persons |
| Leser-Trelat sign | Sudden appearance of multiple seborrheic keratoses, indicates an underlying malignancy (GI, lymphoid) |
| Pemphigus vulgaris | Desmosome targeted by autoimmune IgG against Desmoglein 3 Acantholysis - intraepidermal bullae causing flaccid blister involving the skin and oral mucosa Mouth Nikolsky's sign - separation of epidermis upon manual stroking of skin [DAMN is a vulgar word] |
| Bullous pemphigoid | Autoimmune disorder with IgG antibody against hemidesmosomes (epidermal BM) Linear immunofluorescence Eosinophils within tense blisters Spares oral mucosa Negative Nikolsky's sign - skin doesn't fall off when you stroke it |
| Dermatitis herpetiformis | Pruritic papules, vesicles, and bullae on extensor surface IgA deposits/neutrophils at tips of dermal papillae Assoc with Celiac disease |
| Erythema multiforme | Infections - Mycoplasma pneumoniae, HSV Drugs - sulfa, β-lactams, phenytoin Cancers Autoimmune diseases Multiple types of lesions: macules, papules, vesicles, target lesions |
| Stevens-Johnson syndrome | Fever, bulla formation and necrosis, sloughing of skin, and a high mortality rate 2 mucus membranes are involved (eyes, mouth, etc) - lesions may appear like targets Assoc w adverse drug rxn [CLAPPERS] |
| Toxic epidermal necrolysis | Severe Stevens-Johnson syndrome > 30% of the body surface area |
| Which drugs cause SJS? | Carbamazepine, Lamotrigine, Allopurinol, Phenytoin, Phenobarbital, Penicillin, Ethosuximide, RASH, Sulfa drugs [CLAPPPERS] |
Skin disorders (Misc. and infectious)
| Question | Answer |
|---|---|
| Acanthosis nigricans | Epidermal hyperplasia causing symmetrical, hyperpigmented, velvety thickening of skin on neck or armpits Assoc w hyperinsulinemia (diabetes, obesity, Cushing's syndrome) visceral malignancy hypothyroidism acromegaly polycystic ovary disease |
| Actinic keratosis | Premalignant lesions caused by sun exposure Small, rough, erythematous or brownish papules or plaques Risk of squamous cell carcinoma is proportional to degree of epithelial dysplasia |
| Erythema nodosum | Inflammatory lesions of subcutaneous fat, usually on anterior shins Assoc w sarcoid coccidioidomycosis histoplasmosis TB streptococcal infxns leprosy Crohn's disease |
| Lichen Planus | Pruritic Purple Polygonal Planar Papules and Plaques Sawtooth infiltrate of lymphocytes at dermal-epidermal jct Assoc w Hep C |
| Pityriasis rosea | "Herald patch" first (2-10 cm rash on chest) followed days later by "Christmas tree" distribution Multiple plaques with collarette scale Self-resolving in 6-8 weeks |
| Sunburn | UV irradiation → DNA mutations → apoptosis of keratinocytes UVA - tanning and photoaging UVB - sunburn Can lead to impetigo and skin cancers (Basal cell, squamous cell, and melanoma) |
| Impetigo | Very superficial skin infections Staph a or Strep pyogenes Highly contagious Honey-colored crusting |
| Bullous impetigo | has bullae and is usually caused by Staph a |
| Cellulitis | Acute, painful, spreading infxn of dermis and subQ tissues Usuall Strep pyogenes or Staph a Starts with a break in skin from trauma or other infxn |
| Necrotizing fasciitis | Deeper tissue injury - anaerobic bacteria or Strep pyogenes Crepitus from methane and CO2 production "Flesh-eating bacteria" Bullae and purple color |
| Staphylococcal scalded skin syndrome (SSSS) | Exotoxin destroys keratinocyte attachments in stratum granulosum only (vs toxic epidermal necrolysis which destroys epidermal-dermal jct) Fever, generalized erythematous rash w sloughing of upper layers - heals completely Newborns and children |
| Hairy leukoplakia | White, painless plaques on tongue - cannot be scraped off EBV mediated Occurs in HIV positive pts |
Skin cancer
| Question | Answer |
|---|---|
| What is the most common skin cancer? | Basal cell carcinoma |
| Locally invasive but never metastasizes | Basal cell carcinoma |
| Pink, pearly nodules w rolled borders and central crusting or ulceration | Basal cell carcinoma |
| Commonly with telangiectasias | Basal cell carcinoma |
| nonhealing ulcers with infiltrating growth | Basal cell carcinoma |
| scaling plaque | Basal cell carcinoma |
| Palisading nuclei | Basal cell carcinoma |
| Second most common skin cancer | SCC |
| Immunosuppression | SCC |
| Arsenic exposure | SCC |
| Commonly on face, lower lip, ears, and hands | SCC |
| Maybe LNs, but rare metastasis | SCC |
| Chronic draining sinuses | SCC |
| Ulcerative red lesions with scaling | SCC |
| Actinic keratosis is a precursor | SCC |
| Keratoacanthoma | SCC variant - grows rapidly (4-6 weeks) and may regress spontaneously |
| Significant risk of metastasis | Melanoma |
| S-100 tumor marker | Melanoma |
| Fair-skinned persons are at ↑ risk | Melanoma |
| Depth of tumor correlates with risk of metastasis | Melanoma |
| ABCDEs of melanoma | Asymmetry Border irregularity Color variation Diameter > 6mm Evolution over time |
| Activating mutation in BRAF kinase | Melanoma |
| vemurafenib | Melanoma in pts with BRAF V600E mutation |
| pigmented | Melanoma |
| Which growth pattern increases the risk of melanoma metastasis? | Active vertical growth (Down into the deep dermis) |
| Blue lesion under the nail, tender to touch | Glomangioma (SM cell tumor) |
