Dermatology


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) |