DIT review - MSK 3 Flashcards
Describe histologic features of psoriasis
- Acanthosis (epidermal hyperplasia)
- Increase in stratum spinosum and decrease in stratum granulosum
- Parakeratosis (hyperkeratosis with retention of keratinocyte nuclei in the stratum corneum)
- Munro microabscesses (neutrophils within the stratum corneum)
- Auspitz sign (pinpoint bleeding due to thinning of epidermis above elongated dermal papilla)
Describe gross appearance of seborrheic keratosis
- Raised, discolored plaques that have a coin-like, “waxy/greasy” appearance
- “Stuck on”
Describe histology of seborrheic keratosis
Keratin pseudocysts
What is Lesser-Trelat sign
- multiple seborrheic keratosis appearing suddenly
- Suggestive of GI malignancy
Describe defect behind albinism
- Congenital lack of pigment due to enzyme defect (e.g. tyrosinase) that impairs melanin production
- Normal melanocyte number with decreased melanin production
- Increased risk of skin cancer
Describe defect behind vitiligo
Localized loss of skin pigment due to autoimmune destruction of melanocytes
What are pathogens that cause impetigo
- Superficial bacterial skin infection
- Usually due to Staph aureus or Strep pyogenes
- Honey-colored crusting
What is Erysipelas
- Infection involving upper dermis and superficial lymphatics
- Usually from Strep pyogenes
- Well-define demarcation between infected and normal skin
Pathogens and skin layers involved in cellulitis
- Acute, painful spreading of infection to deeper dermis and subcutaneous tissue
- Usually from Strep pyogenes or staph aureus
In what skin disorder do you see crepitus
Necrotizing fasciitis
- Results in crepitus from the methane and CO2 production
In what skin layer does epidermolysis occur in staph scalded skin syndrome
- Results in epidermolysis of stratum granulosum
- Leads to sloughing of skin (+Nikolsky sign)
What pathogen is the cause of hairy leukoplakia
Ebstein Barr virus (EBV)
What is seen on histology in molluscum contagiosum
- Cytoplasmic inclusions within keratinocytes (molluscum bodies)
Describe histology of pemphigys vulgaris
- Acantholysis of stratum spinosum
- Basal layer remains attached = “tombstone” appearance
Describe immunofluorescence of pemphigus vulgaris
- Immunofluorescence will have a fish net appearance à IgG and C3 deposits in a “chicken wire” pattern
What is the defect in dermatitis herpetiformis
- Deposits of IgA at tips of dermal papillae
Presentation and disease associated with dermatitis herpetiformis
- Pruritic papules, vesicles, and bullae (often found on elbow)
- Associated with Celiac disease
What layer of the skin is seperated in SJS?
Epidermal-dermal junction
Classic presenation of SJS?
- Fever, bullae, necrosis, targetoid lesions
- Sloughing of skin at epidermal-dermal junction
- Usually 2 mucus membranes involved
Drugs that cause SJS?
- Seizure medications (Ethosuximide, Carbamazepine, Lamotrigine, Phenytoin, Phenobarbitol)
- Sulfa medication
- Penicillin
- Allopurinol
What defines Toxic epidermal necrolysis (TEN)
More severe form of Stevens-Johnson that involves >30% of body surface
Describe presentation of Lichen planus
- 6 P’s = pruritic, purple, polygonal, planar, papules and plaques
- Wickham striae (reticular white lines) = mucosal involvement
- Think of a witch (idk why Lichen makes me think of witches)
- Witches wear purple and have a bunch of warts – 6 Ps
- Wicken = Wickham striae
Histology of Lichen planus
- Inflammation of dermal-epidermal junction
- Saw-tooth appearance
- Witches torture people = sawtooth
What are hyperkeratotic scaly plaque, often appearing on face, back, or neck
Precursor to squamous cell carcinoma
Actinic keratosis
