Rash Flashcards
rash definition
inflammatory skin eruption
steps for constructing a ddx for rash in young adult
- identify primary lesion
- determine global reaction pattern
- distribution of lesions
primary lesion definition
initial lesion that has not been altered by trauma or manipulation, and has not regressed
secondary lesion definition
develops as the disease evolves or as the patient damages the lesion
please take this time to review the types of primary lesions and what defines them
yay! you did it!
atrophy
a depression in the skin resulting from thinning of the epidermis, dermis, and/or subcutaneous fat
crust
a collection of dried blood, serum, and/or cellular debris
erosion
a focal loss of epidermis that does not penetrate below the dermal-epidermal junction and therefore can heal without scarring
lichenification
thickening of the epidermis resulting from repeated rubbing, appearing as accentuation of the skin marking
scale defintiion
excess dead epidermal cells
may be find, silvery, greasy, dequamative or adherent
scar
abnormal formation of connective tissue, implying dermal damage
ulcer
focal loss of full-thickness epidermis and partial to full-thickness dermis, which often heals with scarring
what are the types of global reaction patterns
papulosquamous eruptions
folliculopapular eruptions
dermal reaction patterns
purpura and petechiae
nonpalpable purpura
blistering disorders
papulosquamous eruptions definition
papules and plaques with scale
a type of global reaction pattern
folliculopapular eruptions definition
papules forming around the area of skin that has hair distribution
a type of global reaction pattern
dermal reaction patterns definition
a type of global reaction pattern
papules, plaques, nodules that have epidermal changes such as scales
smooth primary lesions that can have secondary changes to them
purpura and petechiae reaction pattern definition
are these lesions elevated?
discolourations due to blood leaking out of vessels
can be raised when you palpate the skin surface
nonpalpable purpura reaction pattern definition
are these lesions elevated?
bruising due to bleeding that is not raised
blistering disorders definition
a type of global reaction pattern
fluid filled lesions
includes pus-filled lesions
during the dermatological physical exam, what features should you note?
general shape
size
colour
margination
palpation - consistency, deviation of temperature, mobility, tenderness, depth of lesion
number
arrangement - grouped or disseminated
confluence
distribution - isolated, localized vs regional vs generalized, pattern
confluence definition
if the multiple lesions flow into each other
if they do not, they are discrete lesions
localized vs regional vs generalized definitions
all ways of describing distribution
localized - one spot on the body
regional - one region
generalized - head to toe, all over the body
what do ABCDE stand for in evaluating for melanoma and dysplastic nevi
Asymmetry
Irregular Borders - ill defined borders higher risk for melanoma
Variegated Colour - more shades of colour is more concerning
Diameter - >6mm higher risk for malignancy
Evolution/enlargement - quickly changing over time higher risk
what types of clinical and laboratory aids are used in dermatological diagnosis
magnification with hand lens
oblique lighting
subdued lighting
wood lamp/UV long wave light/black light
diascopy
dermascopy/epiluminescence microscopy
what clinical tests are used in dermatology
patch testing
prick testing
skin scraping
biopsy - punch biopsy and excisional biopsy
how is magnification with hand lens used in dermatology
a hand lens or binocular microscope is used to view lesions
how is oblique lighting used in dermatology
used to view degrees of elevation or depression in a lesion
done in a darkened room
how is subdued lighting used in dermatology
used to enhance the contrast between circumscribed hypo- or hyper-pigmented lesions and normal skin
involves slightly dimming the lighting
how is a wood lamp/UV long wave light/black light used in dermatology
what specific conditions can it help identify
can pick up fluorescent pigments and subtle colour differences of melanin pigmentation
vitiligo presents as amelanotic
tinea capitits and tinea verisolour can sometimes be visualized
tinea corporis can NOT be visualized with the wood lamp
porphyrias, erythrasama, and pseudomonas bacterial infections can be visualized
how is diascopy used in dermatology
by firmly pressing a microscopic slide or glass spatula over a skin lesion, the examiner determines whether the red colour of a macule or papule is due to dilation (erythema) or due to the extravasation of blood (purpura) that does not blanch
when you press firmly on the lesion with the glass slide, the skin should blanch if redness is due to capillary dilation because you press all the blood away from the lesion
how is dermascopy used in dermatology
a hand lens with a built in lighting and magnification of 10x to 30x is used and allowed for inspection of deeper layers of the epidermis and beyond
helps to distinguish between a benign and malignant lesion
how is patch testing used in dermatology
confirms a diagnosis of allergic contact sensitization and identify the agent that caused the allergic reaction
substances to be tested are placed in shallow cups called Finn chambers and taped onto the skin then left for 24-48 hours
contact hypersensitivity will show as a papular vesicular reaction that will develop within 48-72 hours when the test is read
how is prick testing used in dermatology
used to determine type 1 allergies
a drop of solution containing the allergen is placed on the skin and pierced through with the needle
a positive result would be a wheal appearing within 20 minutes
caution: the patient must be under constant supervision due to possibility of anaphylaxis
how is skin scraping used in dermatology
what are the types and what are they used for
- 2 types: dermatophyte/KOH collection and microbiology culture and sensitivity specimen handling biopsy
- dermatophyte/KOH collection used for microscopic examination for mycelia of the vesicles or scales or in the hair, so we can view the hyphae and spores
- culture and sensitivity - place the antibiotic tablets on the cultured dish and we can see which types of antibiotic would be most effective for eradicating the bacteria
what types of biopsy are used in dermatology
punch biopsy
excisional biopsy
how is punch biopsy used in dermatology
useful in workup of cutaneous neoplasms, pigmented lesions, inflammatory lesions, and chronic skin disorders
a 3-4mm punch (small tubular knife) cuts through the dermis, epidermis, and subcutaneous tissue to remove a skin sample
how is excisional biopsy used in dermatology
surgical removal of a tumour and some normal tissue around it so you can compare the normal tissue to the lesion to see if the tumor is malignant
- this is the “biopsy of choice” because it serves as a treatment for possible malignancy as part of the diagnostic process
