Flat discoloration < 1cm
Ex: Tinea Versicolor caused by M. furfur "sphaghetti & meatballs appearance"
Macule > 1cm
Elevated skin lesion < 1cm
Ex: Acne Vulgaris
Papule (elevated skin lesion) > 1cm
Small fluid containing blister
Ex: Chicken Pox
Large fluid containing blister
Ex: Bullous pemphigoid
Irregular, raised lesion resulting from scar tissue hypertrophy. Overgrowth of granulation tissue (follows trauma in skin, especially in African Americans)
Ex: T. pertenue (yaws)
Blister containing pus
Dried exudates from a vesicle, bulla, pustule
⇑ thickness of strateum corneum (epidermis)
Hyperkeratosis with retention of nuclei in stratum corneum
Separation of epidermal cells or Loss of cohesion between keratinocytes
Ex: Pemphigus Vulgaris
Epidermal hyperplasia (⇑ spinosum)
Inflammation of the skin
Warts caused by HPV.
Soft, tan colored, cauliflower like lesion.
Epidermal hyperplasia, hyperkeratinosis, koilocytosis.
Verruva vulgaris on hands, condyloma acuminatum on genitals
Common mole. benign
Hives. Intensely pruritic wheals that form after mast cell degranulation. Ex: Type I hypersensitivity
Freckle. Normal number of melanocytes, ⇑ melanin pigment
Atopic dermatitis (Eczema)
Acute Pruritic eruption, commonly on skin flexures. Often associated with other atopic disease (asthma, allergic rhinitis)
Allergic contact dermatitis
Type IV hypersensitivity reaction that follows exposure to allergen (Poison ivy, nickel in jewelry)
Lesions occur at site of contact.
Presentation of Psoriasis
Papules & placques with silvery scaling, especially on knees & elbows
Auspitz sign = bleeding spots when scales are scraped off
Commonly preceded by strep pharyngitis
Associated with nail pitting & PSORIATIC ARTHRITIS
Pathogenesis of Psoriasis
Unregulated proliferation of keratinocytes
Acanthosis with Peraketosis (⇑ stratum spinosum, ⇓ stratum granulosum) - red arrow
Neutrophill collections in stratum corneum - blue arrow
Strong HLA relationship
Presentation of Seborrheic keratosis
Flat, greasy, pigmented squamous epithelial proliferation with keratin-filled cysts.
Lesions occur on head, trunk, & extremities.
Epi of Seborrheic keratosis
Common benign neoplasms of older ppl.
Rapid/Sudden appearance of multiple seborrheic keratoses is a pneotypic marker for STOMACH ADENOCARCINOMA
Pathogenesis of Albinism
Normal melanocyte #
⇓ melanin production due to ⇓ activity of tyrosinase (catalyzes production of melanin)
Also caused by failure of neural crest cell migration during development.
Pathogenesis of Vitiligo
Irregular areas of complete depigmentation.
Autoimmune destruction of melanocytes
Malara Hyperpigmentation associated with pregnancy ("mask of pregancy") or OCP use
Very superficial skin infection
Caused by S. aureus or S. pyogenes
Presentation of Cellulitis
Acute, painful spreading infection of dermis and subcutaneous tissue
Caused by S. pyogenes or S. aureus
Deeper tissue injury spreading across fascial plane
Usually from anaerobic bacteria & S. pyogenes. "Flesh eating bacteria"
Results in crepitus from methane & CO2 production.
Pathogenesis Scalded Skin Syndrome
Exotoxin destroys keratinocyte attachments in the STRATUM GRANULOSOM ONLY
Caused by Staph Aureus
Presentation of Scalded Skin Syndrome
Characterized by fever and generalized erythematous rash with sloughing of the upper layers of the epidermis.
Seen in children & kids
Presentation of Hairy Leukoplakia
White, fuzzy, painless plaques on the tongue that cannot be scraped off.
Occurs in HIV patients
Pathogenesis of Pemphigus Vulgaris
Potentially fatal autoimmune skin disorder where IgG antibodies are made against DESMOSOMES (Anti-epithelial cell antibody)
Presentation of Pemphigus Vulgaris
Acantholysis - Intraepidermal bullae/blister involving the skin & oral mucosa. (oral b4 skin)
+ Nikolsky's sign (separation of epidermis forms new blisters with minimal trauma)
Lab findings in Pemphigus Vulgaris
Immunofluorescence reveals antibodies around cells of epidermis in a reticular or netlike pattern
Pathogenesis of Bullous pemphigoid
Autoimmune disorder with IgG antibody against HEMIDESMOSOMES (epidermal basement membrane, ABs are "bullow" the epidermis)
Lab findings of Bullous Pemphigoid
Shows linear immunoflourscence.
Eosinophils within blisters
Presentation of Bullous Pemphigoid
Large fluid containing blister over the skin but spares oral mucosa
Negative Nikolsky's sign
Pathogenesis of Dermatitis Herpetiformis
Deposits of IgA complexes at the tips of dermal papillae → produces subepidermal vesicles with neutrophils.
Strongly associated with Celiac Dz
Presentation of Dermatitis Herpetiformis
Pruritic papules and vesicles with context malabsorption from celiac Dz
Presentation of Erythema Multiforme
Presents with multiple types of lesions - macules, papules, vesicles, and TARGET LESIONS (red papules with a pale central area).
Pathogenesis of Erythema Multiforme
Associated with infections (Mycoplasma pneumoniae, HSV), drugs (sulfa drugs, β-lactams, phenytoin), cancers, & autoimmune dz
Presentation of Steven Johnson syndrome
Characterized by fever, bulla rash formation & necrosis, sloughing of skin, and high mortality rate
Associations of Steven Johnson Syndrome
Associated with adverse drug reaction.
Antibiotics: Sulfonamides & Penicillins
Anticonvulsants: Phenytoin, Lamotrigine
Presentation of Lichen planus
Pruritic, purple, polygonal papules.
Oral mucosa also produces a fine, white, net-like lesion (Wickham's striae)
Pathology of Lichen planus
Sawtooth infiltrate of lymphocytes at dermal-epidermal junction
Associated w/ HEPATITIS C
Pathology of Actinic Keratosis
Premalignant lesions caused by sun exposure
Small, rough, erythematous or brownsih papules
Risk of carcinoma is proportional to vertical epithelial dysplasia
Presentation of Erythema Nodosum
Inflammatory lesions of subcutaneous fat, usually on anterior shins
Associations of Erythema Nodosum
Associated with Coccidiodomycosis, histoplasmosis, TB, leprosy, streptococcal infections, sarcoidosis.
Presentation of Acanthosis Nigricans
Velvety pigmented skin lesion, commonly in the axilla
Associations with Acanthosis Nigricans
Can be a sign of hyperinsulinemia (Cushings, Diabetes, Insulin receptor deficiency), Polycystic ovarian syndrome, stomach cancer.
Presentation of Pityriasis Rosea
- Initially presents as a single, large, oval, scaly, rose-colored plaque on the trunk ("Herald spot").
- Days or weeks later, a pruritic papular eruption develops on the trunk that follows the lines of cleavage ("Xmas tree distribution")
Presentation of Strawberry Hemangioma
Bright red papules usually around the head/neck
Presents in the first few weeks of life (1/200) births;
Grows rapidly & regresses at 5-8 years age
Tiny bright red papules
Appears in 30s-40s
Does NOT regress