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Impetigo
- Very superficial skin infection
- S. aureus, S. pyogenes
- Highly contagious
- Honey-colored crusting
 - Bullous impetigo has bullae and is usually S. aureus
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Cellulitis
- Acute, painful, spreading infection of dermis and subcutaneous tissue
- S. pyogenes, S. aureus
- Often starts with break in skin from trauma, or from another infection
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Necrotizing fasciitis
- Deeper tissue injury
- anaerobic bacteria, S. pyogenes
- Crepitus from methane and CO2 production
- "Flesh-eating bacteria"
- Causes bullae and purple color to skin
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Staphylococcal scalded skin syndrome (SSSS)
- Exotoxin destroys keratinocyte attachments in the stratum granulosum only
- (vs. toxic epidermal necrosis → destroys epidermal-dermal junction)
- Fever, generalized erythematous rash
- sloughing of upper layer of epidermis
- heals completely
- seen in newborns, children
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Hairy leukoplakia
- White, painless plaques on tongue
- CANNOT be scraped off
- EBV mediated
- Occurs in HIV-positive patients
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Basal cell carcinoma
- Most common skin cancer
- Sun-exposed areas of the body
- Locally invasive, rarely metastatic
- Pink, pearly nodules, commonly with telangiectasias, rolled borders, central crusting or ulceration (A)
- BCC can appear as nonhealing ulcer with infiltrating growth (B)
- Scaling plaque (superficial BCC) (C)
- Basal cell tumors have "palisading" nuclei (D)
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Squamous cell carcinoma
- Second most common skin cancer
- Associations: excessive exposure to sunlight, immunosuppression, arsenic exposure; chronic draining sinuses
- Location: commonly appears on face (E), lower lip (F), ears, hands
- Locally invasive, may spread to LN, rarely metastasize
- Ulcerative red lesions with frequent scale
- Histology: keratin "pearls" (G)
- Actinic keratosis: a scaly plaque; precursor to SCC
- Keratoacanthoma: variant that grows rapidly (4-6 weeks) may regress spontaneously over months (H)
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Melanoma
- Common tumor with significant metastasis risk; depth of tumor correlates with risk of mets
- Tumor marker: S-100
- Associations: sun exposure, fair-skined persons
- Many types: superficial, nodular, lentigo maligna, acrolentiginous
- ABCDs: Asymmetry, Border irregularity, Color variation, Diameter >6mm, Evolution over time
- Activating mutation in BRAF kinase
- Tx
: excision with wide margins; Vemurafenib (BRAF kinase inhibitor) in pts with unresectable melanoma with BRAF V600E mutation
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