Contact dermatitis
- pruritic, oozing rash with vesicles and edema
- arises upon exposure to allergens (e.g., poison ivy, nickel, drugs, etc.)
- treatment: remove allergen, topical glucocorticoids (to reduce inflammatory response)
4 types of hypersensitiviy
Type I: allergy (immediate, inflammatory)
Type II: cytotoxic (antibody-mediated)
Type III: Immune complex diseases
Type IV: delayed hypersensitivity, cell-mediated immune memory response (antibody-dependent), contact dermatitis (e.g., poison ivy)
Acne vulgaris
- due to chronic inflamm of hair follicles/sebaceous glands
- occur either with a hormone-associated increase in sebum production and keratin production, or bc of infection w P. acnes which break down sebum into proinflammatory fatty acids
- treatment: benzoyl peroxide (antimicrobial) and vitamin A derivatives (to reduce keratin production)
Psoriasis
- Presents as salmon-colored plaques with silver scale
- tends to erupt on extensor surfaces (knees, elbows, etc), & nails
- due to excessive keratinocyte proliferation w possible autoimmune etiology (HLA-C gene)
- Auspitz sign: pin pricks of bleeding when scale is removed from extended dermal papillae
- Histological features: Acanthosis of the corneum (forms the scale), Parakeratosis (nuclei retention in the stratum corneum), Munro microabcesses (collections of neutrophils in the stratum corneum)
- treatment: corticosteroids, UV light with psoralen or immune modulating therapy
Lichen Planus
- Pruritic, planar, polygonal purple papules, often w reticular white lines on their surface (Wickham striae)
- commonly found on wrists, elbows, and oral mucosa
- associated with hep C virus but exact cause is unknown
Pemphigus Vulgaris
- Autoimmune destruction of desmosomes between keratinocytes (spinosum)
- IgG antibody against desmoglein (Type II hypersensitivity)
- Presents as skin and oral mucosa bullae
- Thin-walled bullae rupture easily (Nikolsky sign); become shallow erosions with dried crust
Palisading is characteristic of what type of skin lesion?
Basal cell carcinoma
What are telangiectasis, and what what diagnosis are they associated?
They are dilated super epidermal blood vessels, and they are often seen in basal cell carcinomas.
Where do squamous cell carcinomas usually present?
On sun exposed surfaces.
What is the ABCDEs of melanoma?
Asymmetry Border Color Diameter Elevation or Evolution
What are the “seeds” in verruca vulgaris?
Verruca vulgaris is the mom on wart, and the “seeds” in the lesions are due to thrombosis capillaries because the warts have out-grown their blood supply.
Define acantholysis.
The loss of cell adhesion (e.g., autoimmune targeting desmoglein of desmosomes).
Targetoid skin lesions are characteristic of which skin lesions?
Lyme’s disease and erythema multiforme.
Define acanthosis.
Thickening of the epidermis via hyperplasia.
What is Auspitz sign, and what is it characteristic of?
Pin-sized blood spots when scales on the skin are peeled away. Characteristic of psoriasis.
What is Nikolsky’s sign?
A popped blister, where the top layers of skin have been removed.
Immunofluorescence staining will be positive for which disorders? What distinguishes them?
Pemphigus vulgaris and bullous pemphigus.
- Autoantibodies (IgG and C3) target desmoglein (desmosomes) in pemphigus vulgaris, so staining will be green throughout the stratum spinosum.
- Autoantibodies target hemidesmosomes and stain green surrounding the basal layer.
A hyperpigmented papule dimples downward into the skin when pinched. What is it, and is it benign or malignant?
Dematofibroma. Benign.
What are dermatofibromas also called?
Fibrous histiocytoma.
Where do the basal cells originate epidemiologically?
Basal cells arise from the neural crest. The rest of the epidermis arises from the ectoderm.
Do basal cell carcinomas metastasize?
No, but they are locally invasive. They will grow down into the dermis and even into bone. The mass may get bigger, but it will not break pieces off and travel elsewhere to grow.
Why don’t sores from basal and squamous carcinomas heal?
They are malignant and have undergone malignant differentiation. They don’t heal normally.
What is the classic clinical presentation for squamous cell carcinoma?
It most often presents as a nodule with central ulceration and a pink, elevated, indurated border that does not heal spontaneously.
Do squamous cell carcinomas metastasize?
Not usually on keratinized skin. It’s much more likely when they appear on the lip or genitals.
