Pathoma chapter 19 Skin
Terms in this set (43)
In what layer of the epidermis are the stem cells?
What layer of the dermis/epidermis is notable for its connection via desmosomes?
Atopic dermatitis is what type of hypersensitivity reaction?
type I (like asthma, allergic rhinitis)
What bacterium is usually responsible for acne?
Propionibacterium acnes (or, "P. acnes")
-usually follows inflammation of the hair follicle and sebaceous gland, causes production of lipases
How do Vitamin A derivatives help in the treatment of acne?
Vitamin A crucial for maintenance of keratin layer, so having enough VitA helps prevent excess keratin sloughing/dysfunction that would block sebaceous glands/hair follicles and clog pores
Psoriasis is associated with what 4 histological findings? What about MHC complexes?
1) epidermal hyperplasia (proliferation of keratinocytes)
2) Parakeratosis (hyperkeratosis with retention of keratinocyte nuclei in stratum corneum)
3) neutrophils in stratum corneum (Munro microabscesses)
4) Thinning of epidermis above elongated dermal papillae (Auspitz sign: bleeding when scales are pulled off)
HLA-C associated with psoriasis
What are the 5 Ps of Lichen Planus?
What's the key histopath finding of lichen planus? What else is it associated with?
inflammation at the dermal/epidermal junction (makes a sawtooth appearance)
-associated with chronic Hep C infection
What's the pathological basis of Pemphigus Vulgaris?
-breakdown of desmosomes leads to blisters
-mediated by IgG against desmoglein
**characterized by IgG surrounding keratinocytes, apparent by immunofluorescence
What autoimmune disease can cause blisters of skin and oral mucosa?
Pemphigus Vulgaris - often involves oral mucosa!!
So...what's the difference in pathology of Pemphigus Vulgaris and Bullous Pemphigoid?
PV: IgG against desmoglein in desmosomes; leads to separation of stratum spinosum from stratum basalis (which stays attached to basement membrane)
BP: IgG against basement membrane & thus breakdown of hemidesmosomes; leads to separation of stratum basalis from dermis (entire epidermis separated from dermis!)
***Note: PV involves oral mucosa, BP does NOT involve oral mucosa
Which of Pempigus Vulgaris and Bullous Pemphigoid has blisters that rupture easily?
PV blisters rupture easily - thinner layer of epidermis since it does not include basalis
Why does Dermatitis Herpetiformis result in a bunch of little vesicle lesions?
IgA is deposited at tip of dermal papillae, which leads to those separated, few millimeter thick vesicles
Dermatitis Herpetiformis has a strong associated with...
(IgA mediated - same antibody against gluten)
A patient presents with severe sloughing of skin that resembles a burn, but the patient says he has not had any exposure to hot water or chemicals. What could be going on?
Stevens Johnson Syndrome / Toxic Epidermal Necrolysis
-most often arises due to adverse drug reaction
An elderly patient presents with a raised, discolored plaque. What is it most likely?
Keratinic pseudocysts are characteristic of what condition?
A patient present with one or two seborrheic keratoses that "have been there a long time". Is the condition serious?
no - completely benign
A patient presents with sudden onset of multiple seborrheic keratoses that "just came out of nowhere". Is the condition serious?
YES - could be indicative of underlying GI carcinoma
-called "Leser-Trelat" sign
Acanthosis nigricans is associated with what 2 conditions?
1) insulin resistance (type II diabetes)
2) carcinoma (often GI)
What is the greatest risk factor for developing basal &/or squamous cell carcinoma?
prolonged exposure to UVB light
Why do patients with xeroderma pigmentosum have a greater risk for basal & squamous cell carcinoma?
UVB can cause thymine dimers for form
patients with XP do not have nucleotide excision repair enzymes, so...
-when thymine dimers form, patient with XP is unable to repair them and thus they have basal cell carcinoma susceptibility
What is a very common location for the occurrence of basal cell carcinoma?
A patient on immunotherapy is most likely to develop what neoplasm?
What is a very common locaiton for the occurrence of squamous cell carcinoma?
Actinic keratosis increases the risk of development of what neoplasm?
Melanocytes come from what embryological origin?
neural crest cells
What the hell is vitiligo?
autoimmune destruction (locally) of melanocytes (so, loss in pigmentation in that area)
What produces albinism?
congenital absence of tyrosinase, which impairs melanin production
Why is a freckle darker?
increased number of melanosomes
NO INCREASED MELANOCYTES
What's melasma, and what's it associated with?
melasma = hyperpigmentation of cheeks
associated with pregnancy and OCT
What are the most common moles in children and adults?
children: junctional nevus - proliferation of melanocytes at dermal/epidermal border
adults: intradermal nevus - proliferation of melanocytes sub-epidermis (basically, the junctional one invades - called a "compound nevus" - then the junctional melanocytes die, and then you just have the INTRA dermal part)
How do you distinguish nevus from melanoma?
Borders - irregular
Color - not uniform
Diameter > 6mm
What are the 4 types of melanoma? Which is most common? Which has the worst prognosis?
lentigo maligna: radial growth only - good prognosis
superficial spreading: radial growth primarily with late vertical growth - good prognosis, MOST COMMON
nodular: early vertical growth - poor prognosis
Acral lentiginous - arises on palms/soles often in dark skinned individuals, not related to UV exposure
Most important characteristic for prognosis of melanoma?
depth of extension into dermis (the farther down it goes, the more likely it is to metastasize, the worse the prognosis)
A child presents with erythematous macules that progress to pustules on his face. What is the likely diagnosis?
impetigo - usually caused by S. aureus OR S. pyogenes
A child presents with red, tender, swollen rash and fever. What is the likely diagnosis?
Cellulitis - usually causd by S. aureus OR S. pyogenes
What's the difference in pathology between impetigo and cellulitis?
impetigo - just epidermis
cellulitis - infection of dermis; accompanied by fever
3 risk factors for cellulitis:
2) recent surgery
3) insect bite
Which of cellulitis/impetigo are you more scared of? Why?
cellulitis - can lead to necrotizing fasciitis
What's the pathology of Staphylococcal Scalded Skin Syndrome?
S. aureus produces exfoliatin A & B that causes separation of stratum granulosum from the rest of the epidermis
How is SSSS different from TEN?
SSSS = staphylococcal scalded skin syndrome
TEN = toxic epidermal necrolysis
***Differentiate by layers involves
SSSS: stratum granulosum - very superficial
TEN: dermal/epidermal junction - deeper layers involved
Molluscum Contagiosum is due to infection with...
-sexually transmitted in adults
-most often arises in children, though