Pathoma - Skin - Inflammatory and Blistering dermatoses Flashcards
What are the 4 layers of epidermis, from basement membrane to surface?
Stratum basalis (stem cells)
Stratum spinosum (desmosomes b/w keratinocytes)
Stratum granulosum (granules)
Stratum corneum (keratin in anucleate cells)
What type of HSR is atopic dermatitis (e.g. eczema)
Type I - often associated with asthma and allergic rhinitis
What type of HSR reaction is contact dermatitis?
Type IV (cell-mediated)
Describe the pathogenesis of acne
Hormone associated increase in sebum production and excess keratin production block follicles, forming comedones
Propionibacterium acnes infection produces lipases that break down sebum, releasing inflammatory fatty acids, resulting in pustule or nodule formation
What is the treatment for acne?
Benzoly peroxide (antibiotic)
Vitamin A derivatives (retinoids) - reduce keratin production
What is the term for well-circumscribed, salmon-colored plaques with silvery scale, usually on extensor surfaces and scalp
Psoriasis
Describe the histology of psoriasis
Acanthosis (epidermal hyperplasia)
Parakeratosis (excess keratin with retention of nuclei in the stratum corneum)
Neutrophils within the stratum corneum (Munro microabscesses)
Thinning of epidermis above elongated dermal papilla (decreased stratum granulosum)
What is Auspitz sign and what disease is it seen in
“Pinpoint” bleeding when scales of Psoriasis are picked off due to thinning of epidermis above dermal papillae
Describe the appearance of Lichen Planus
5 P’s
Pruritic, Purple, Polygonal, Planar papules and plaques
What are Wickham striae and what disease are they associated with?
Mucosal involvment of Lichen Planus
Describe histology of Lichen Planus
Inflammation of the dermal-epidermal junction with “saw-tooth” appearance
What chronic disease is Lichen Planus associated with?
Hepatitis C
What is the defect in Pemphigus vulgaris?
Autoimmune destruction of desmosomes due to IgG against desmoglein (type II HSR)
Describe the histology and blisters of pemphigus vulgaris
Acantholysis (seperation) of stratum spinosum (normally connected by desmosomes)
Basal cell layer remains attached to basement membrane via hemidesmosomes, giving a “tombstone” appearance
Leads to intra-epidermal blisters which are thin-walled and rupture easily
What is the defect in bullous pemphigoid?
Autoimmune destruction of hemidesmosomes (IgG) between the basement membrane and basal cells
Describe the histology and blisters of bullous pemphigoid
Subepidermal blisters that seperate the basal cell layer from the basement membrane
Bullae do not rupture easily
What is Nikolsky sign and what diseaase is it involved in?
Seperation of epidermis upon manual stroking of skin
+ in pemphigus vulgaris
Differentiate between pemphigus vulgaris and bullous pemphigoid
Pemphigus vulgaris
- IgG against desmosomes
- Oral mucosa involved
- Blisters rupture easily
Bullous pemphigoid
- IgG against hemidesmosomes
- Oral mucosa NOT involved
- Blisters do not rupture easily
Describe the defect in dermatitis herpetiformis
Deposition of IgA at the tips of dermal papillae
Leads to pruritic vesicles and bullae that are grouped
What chronic disease is associated with dermatitis herpetiformis?
Celiac disease (IgA antibodies against gluten cross-react)
Describe the apperance of erythema multiforme
Targetoid rash and bullae
Targetoid appearance due to central epidermal necrosis surrounded by erythema
Most common causes of erythema multiforme
HSV infection
Others: Mycoplasma, drugs, autoimmune, malignancy
Describe the presentation of Stevens-Johnson syndrome and the location of acantholysis
Fever, targetoid rash, bullae, necrosis, skin sloughing, usually involving 2 mucus membranes
Sloughing of skin occurs at dermal-epidermal junction
