Pathoma - Skin - Inflammatory and Blistering dermatoses

Question 1

What are the 4 layers of epidermis, from basement membrane to surface?

Answer 1

Stratum basalis (stem cells)

Stratum spinosum (desmosomes b/w keratinocytes)

Stratum granulosum (granules)

Stratum corneum (keratin in anucleate cells)

Question 2

What type of HSR is atopic dermatitis (e.g. eczema)

Answer 2

Type I - often associated with asthma and allergic rhinitis

Question 3

What type of HSR reaction is contact dermatitis?

Answer 3

Type IV (cell-mediated)

Question 4

Describe the pathogenesis of acne

Answer 4

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

Question 5

What is the treatment for acne?

Answer 5

Benzoly peroxide (antibiotic)

Vitamin A derivatives (retinoids) - reduce keratin production

Question 6

What is the term for well-circumscribed, salmon-colored plaques with silvery scale, usually on extensor surfaces and scalp

Answer 6

Psoriasis

Question 7

Describe the histology of psoriasis

Answer 7

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)

Question 8

What is Auspitz sign and what disease is it seen in

Answer 8

“Pinpoint” bleeding when scales of Psoriasis are picked off due to thinning of epidermis above dermal papillae

Question 9

Describe the appearance of Lichen Planus

Answer 9

5 P’s

Pruritic, Purple, Polygonal, Planar papules and plaques

Question 11

What are Wickham striae and what disease are they associated with?

Answer 11

Mucosal involvment of Lichen Planus

Question 12

Describe histology of Lichen Planus

Answer 12

Inflammation of the dermal-epidermal junction with “saw-tooth” appearance

Question 13

What chronic disease is Lichen Planus associated with?

Answer 13

Hepatitis C

Question 14

What is the defect in Pemphigus vulgaris?

Answer 14

Autoimmune destruction of desmosomes due to IgG against desmoglein (type II HSR)

Question 15

Describe the histology and blisters of pemphigus vulgaris

Answer 15

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

Question 16

What is the defect in bullous pemphigoid?

Answer 16

Autoimmune destruction of hemidesmosomes (IgG) between the basement membrane and basal cells

Question 17

Describe the histology and blisters of bullous pemphigoid

Answer 17

Subepidermal blisters that seperate the basal cell layer from the basement membrane

Bullae do not rupture easily

Question 18

What is Nikolsky sign and what diseaase is it involved in?

Answer 18

Seperation of epidermis upon manual stroking of skin

+ in pemphigus vulgaris

Question 19

Differentiate between pemphigus vulgaris and bullous pemphigoid

Answer 19

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

Question 20

Describe the defect in dermatitis herpetiformis

Answer 20

Deposition of IgA at the tips of dermal papillae

Leads to pruritic vesicles and bullae that are grouped

Question 21

What chronic disease is associated with dermatitis herpetiformis?

Answer 21

Celiac disease (IgA antibodies against gluten cross-react)

Question 22

Describe the apperance of erythema multiforme

Answer 22

Targetoid rash and bullae

Targetoid appearance due to central epidermal necrosis surrounded by erythema

Question 23

Most common causes of erythema multiforme

Answer 23

HSV infection

Others: Mycoplasma, drugs, autoimmune, malignancy

Question 24

Describe the presentation of Stevens-Johnson syndrome and the location of acantholysis

Answer 24

Fever, targetoid rash, bullae, necrosis, skin sloughing, usually involving 2 mucus membranes

Sloughing of skin occurs at dermal-epidermal junction

Question 25

Differentiate SJS from Toxic epidermal necrolysis (TEN)

Answer 25

TEN is a more severe form of SJS that involves > 30% of body surface