Common Dermatoses III and IV Flashcards
Mechanism of lichen planus
Unknown antigen, but cell-mediated immunity (tons of T cells found in the skin lesion biopsies)
What is the lichenoid reaction pattern on pathology?
Huge infiltration of lymphocytes lined up at the dermal-epidermal junction
2 known possible causes of lichen planus
- Hep C (especially in oral lichen planus)
- medication
What are the 4 P’s of lichen planus?
purple, papules, polygonal, pruritic
Most common sites for lichen planus
Wrist flexors (forearm surface), ankles, legs, genitalia
Lichen planus treatment
Self-limiting, usually goes away on its own in about 15 months
-topical steroids can be used if needed
What is tinea dermatophytosis?
(a) where does the infective organism live?
(b) how is it spread?
Tinea dermatophytosis = Ring worm
(a) Hangs in the stratum cornea => only in keratinized tissue (epidermis, hair, nails)
(b) Spread thru soil, animals, or other humans
Diagnostic tool for tinea dermatophytosis
See fungi w/ KOH prep
Septated, branching hyphae => tinea dermatophytosis (fungi causing ring worm)
Spaghetti and meatball’ appearance of hyphae and spores = yeast malassezia furfur = causes tinea versicolor
Treatment for tinea dermatophytosis
(a) Response to steroids
Treat ring worm w/ topical or oral (second line) antifungals
(a) Gets worse when given steroids
How to differentiate dysplastic nevi and malignant melanoma on appearance
Often very hard! => need to do biopsy
Dysplastic nevi often don’t fit the ABCDE pattern of benign lesions. Need to do skin exams very regularly (and w/ pictures) to see which lesions require biopsy
Why are dysplastic nevi dangerous?
6x higher risk of melanoma
-pts w/ sporadic dysplastic nevi + FHx of dysplastic nevi + FHx of melanoma = risk of melanoma approaches 100% by age 75
How to manage pts w/ dysplastic nevi
Very frequent skin checks, often use total body photographs to compare and note any changes
-biopsy the moles that you can’t clinically distinguish from melanoma => get pathologic confirmation that not cancerous
What is a woods lamp?
Distinguish hypopigmentation and depigmentation
What two things do you want to ask a pt w/ psoriasis
- joint pain (psoriatic arthritis)
- counsel on CVD (psoriasis pts have increased risk for CVD)
What is dyshydrotic eczema?
Not sweating! Recurrent, bilateral, symmetrical vesicular eruptions on hands and feet
- vesicles classically on side of fingers w/ deep seeded ‘tapioca pudding’ sppearance
- really itchy
