Dermatology Flashcards
What are the two descriptive terms for flat skin lesions?
What is the difference between these two?
Macules and Patches
The difference is their size
If less than or equal to 0.5cm it is termed a macule
Anything greater than 0.5cm is termed a patch
Smoothed raised lesions can be classified as cysts, nodules, papules and plaques.
Describe each of these
Cysts - A closed cavity or sac containing fluid or semisolid material
Nodules - A dermal or subcutaneous firm, well-defined lesion usually greater than 0.5 cm in diameter.
Papules - A discrete, solid, elevated body usually less than or equal to 0.5 cm in diameter. Papules are further classified by shape, size, color, and surface change.
Plaques - A discrete, solid, elevated body usually broader than it is thick, measuring more than 0.5 cm in diameter. Plaques may be further classified by shape, size, color, and surface change.
‘Surface change’ in skin can be classified as either crust or scale. What is the difference between these two?
Crust - A hardened layer that results when serum, blood, or purulent exudate dries on the skin surface. Crusts may be thin or thick and can have varying color.
Scale - results from excess stratum corneum (the most superficial layer of the skin) that accumulates in flakes or plates. Scale usually has a white or gray color.
What are the three types of fluid-filled skin lesions?
What are the differences between these three?
Bullae - fluid-filled blisters greater than 0.5 cm in diameter. Fluid can be clear, serous, hemorrhagic, or pus filled.
Vesicles - fluid-filled cavity or elevation less than or equal to 0.5 cm in diameter. Fluid may be clear, serous, hemorrhagic, or pus filled.
Pustules - A circumscribed elevation that contains pus. Pustules are usually less than or equal to 0.5 cm in diameter.
What layers of the skin do the following affect?
Bullous pemphigoid
Pemphigus vulgaris
Bullous impetigo
Bullous pemphigoiD - sub-dermal blisters
Pemphigus vulgaris - intra-epidermal blisters
Bullous impetigo - sub-corneal blisters
Pemphigus/Pemphigoid blisters are deep, lift up the entire epidermis and are resistant to rupturing
Pemphigus/Pemphigoid blisters are intra-epidermal and more prone to rupture, as such in clinics you may see them more as erosions rather than blisters
Pemphigoid blisters are deep and resistant to rupture
Pemphigus blisters are more prone to rupture and may present with erosions
When clinically investigating the nature of blisters, what would you do to confirm the following?
Infection
Porphyria
Contact dermatitis
Autoimmune
Infection - bacterial culture and microscopy, PCR, viral culture, serology
Porphyria - porphyrin studies
Contact dermatitis - patch testing
Autoimmune - biopsy with IMF
What is the most common of all the autoimmune blistering diseases?
Bullous pemphigoid
Incidence increases with age
What is the autoimmune pathophysiology of bullous pemphigoid?
IgG react with antigens in the basement membrane (BM) and with hemidesmosomes anchoring basal cells to BM
This results in local complement activation and tissue damage, with subdermal bullae forming
How is bullous pemphigoid treated
a) locally
b) generally?
What is the prognosis?
a) potent topical steroids
b) systemic steroids, tetracyclines, methotrexate
Chronic self-limiting condition, with most patients achieving remission in 3-6 months. Relapse is uncommon
How common is pemphigus vulgaris? What age range is most commonly affected?
Very uncommon, may never see it unless working as a dermatologist
Most commonly affects people in middle age
What is Nikolsky’s sign?
It is positive in Bullous Pemphigoid/Pemphigus vulgaris
Nikolsky’s sign is friability of a blister when rubbed with a wooden spatula
It is positive in PV but negative in BP
What are antibodies formed in response to in Pemphigus Vulgaris?
IgG antibodies are formed against desmoglein 3 (membrane protein that helps to maintain desmosome structure)
PV is a lot more difficult to treat than BP. How is PV treated?
What is the mortality associated with PV?
Locally - potent high dose topical steroids and topical anaesthetic creams
Systemicaly - prednisolone +/- another immunosuppressive agent
PV has a mortality rate of 10-20% in treated patients (used to be higher)
How common is Dermatitis Herpetiformis?
What other condition does it overlap with?
What age ranges are affected?
DH is very common
Overlaps with Coeliac Disease
Can affect all ages, majority are young adults
