Acute Dermatoses

Question 1

What are the projections between the dermis and epidermis called?

Answer 1

Dermal papillae

- interact with the epidermal ridges to strengthen adhesion of the dermis and epidermis to each other

Question 2

What are the epidermal derivatives

Answer 2

Nails

Hairs

Sebaceous and sweat glands

Question 3

Cells of the epidermis

Answer 3

Stratified keratinized epithelium

Keratinocytes (most abundant)

Melanocytes

Langerhans cells

Tactile Merkel cells

Question 4

Thick vs thin skin

Answer 4

Based on the density of epidermis

Thick = 400-1400 um

Thin = 75-150 um

Question 5

Layers of the epidermis

Answer 5

Stratum basale
- single layer of basophilic cuboidal or columnar cells at the dermal-epidermal junction

Stratum spinousum
- thickest layer in thin skin with polyhedral cells that also has active synthesizing keratins

Stratum granulosum

• 3-5 layers of flattened cells that undergoes terminal differentiation of keratinization
• cytoplasm is filled with basophilic masses called “keratohyaline granules”

Stratum lucidium

• ONLY found in thick skin
• consists of a thin, translucent layer of flattened eosinophilic keratinocytes held together by desmosomes

Stratum corneum

• consists of 15-20 layers of squamous keratinized cells with Briefringent filamentous keratins
• is the thickest layer in thick skin

Question 6

Eumelanins

Answer 6

Brown/black pigments that are produced by melanocytes

Question 7

What is the primary step in melanin synthesis?

Answer 7

Tyrosine -> (3,4) dihydroxyphenylalanine (DOPA)
- done via tyrosinase activity

DOPA is then further transformed into melanin**

Question 8

What are melanosomes?

Answer 8

Matrix structural proteins that accumulate in vesicles and form elliptical granules
- are about 1um long

The melanosomes get phagocytosed into keratinocytes and accumulate within.

ultimately protect DNA of the living keratinocytes from UV damage and ionizing radiation

Question 9

Langerhan cells

Answer 9

Antigen presenting cells that are derived form monocytes.
- usually seen in the spinous layer and derived from monocytes

They are the professional antigen presenting cells of the skin

Question 10

Lichenification

Answer 10

Thickened rough skin that is usually a result of repeated rubbing

Question 11

Macules

Answer 11

Circumscribed flat lesions distinguished from surrounding skin by color
- are less than 5mm in diameter (if larger = nodules)

Question 12

Plaques

Answer 12

Elevated flat-topped lesions that are usually >5mm in diameter

Question 13

Wheal

Answer 13

Itchy transient and elevated lesions with variable blanching and erythema formed as a result of dermal edema

Question 14

Acanthosis, hyperkeratosis and papillomatosis

Answer 14

Acanthosis = diffuse epidermal hyperplasia

Hyperkeratosis = thickening of the stratum corneum. Usually shows qualitative hyperplasia of keratin also

Papillomatosis = surface elevation caused by hyperplasia and enlargement of contiguous dermal papillae

Question 15

Parakeratosis

Answer 15

Retension of nuclei in the striations corneum of the squamous epithelium
- this is normal on mucous membranes, but pathological on non-mucous membranes

Question 16

Spongiosis

Answer 16

Intercellular edema of the epidermis

Question 17

Acute inflammatory dermatoses

Answer 17

Are acute lesions (days-3 weeks) in duration and are characterized by inflammation, edema and epidermal vascular/subcutaneous injuries

**Are often marked by infiltrates consisting of mononuclear cells rather than neutrophils

Question 18

Urticaria (hives)

Answer 18

Common disorder that leads to dermal microvascular hyperpermeability due to localized mast cell degranulation

Produces wheal plaques that are edamatous and pruritic

Stems from an immediate type 1 hypersensitivity reaction. Mast cells bind to IgE antibodies which are bound to viruses, pollens, foods, drugs, insect venom, etc.
- can also induce IgE-independent urticaria which is caused by opiates an antibiotics

Question 19

Treatment of urticaria

Answer 19

Most respond to antihistamines

- refractory cases = immunosuprrants and MABs

Question 20

Acute eczematous dermatitis

Eczema

Answer 20

Pruritic lesions that are often erythematous and ooze/become crusted
- chronically = raised, scaling plaques

Multiple subtypes
1) allergic contact dermatitis = topical exposure and delayed hypersensitivity

2) atopic dermatitis = defects in the keratinocytes Barrier function defined as skin with increased permeability to substances
* *highly genetic based**

3) drug-related eczematous dermatitis = hypersensitivity to a drug
4) photoeczematous dermatitis = abnormal reaction IV or visible light
5) primary irritant dermatitis = results from exposure to substances that chemically, physically or mechanically damage the skin

Question 21

Allergic contact dermatitis

Answer 21

Triggered by exposure to environmental contact-sensitizing agents
- poison ivy is the classic example

1st exposure = reacts with self-proteins and creates neoantigens that can be recognized by T-cell adaptive immune system
- these neoantigens are processed by epidermal langerhan cells and migrate to draining lymph nodes to present to naive T-cells

2nd exposure = Re-exposure causes activation of memory CD4+ T-lymphocytes and migrates to affected skin sites during course of normal circulation, where they release cytokines and recruits additional inflammatory cells
type-4 delayed Hypersensitivity reaction

Question 22

What other dermatological condition is always present in acute eczematous dermatitis?

Answer 22

Spongiosis (epidermal edema)
- shows superfical perivascular lymphocytic infiltrate

hence why it is sometimes synonymously called spongiotic dermatitis

Question 23

Genetic component to atopic dermatitis

Answer 23

Concordant in 80% of identical twins and 20% in fraternal twins

**often is worse in childhood and gets better in adulthood

Question 24

What is the atopic triad

Answer 24

Asthma, allergic rhinitis and atopic dermatitis

- these three often show up altogether

Question 25

Erythema multiforme

Answer 25

Epithelial injury that is mediated by CD8+-Tcells

Uncommon and is often self-limiting
- is a hypersensitivity response to infections and drugs

Question 26

Infections associated with erythema multiforme

Answer 26

Herpes simplex

Mycoplasma

Fungi species

**Less dangerous

Question 27

Drugs associated with erythema multiforme

Answer 27

Sulfonamides, penicillin, salicylates, anti-malaria drugs

**More dangerous and high risk of SJS and TEN

Question 28

Stevens-Johnson syndrome

Answer 28

Is a systemic, febrile form of erythema multiforme
- by itself not overly dangerous but makes patients prone to secondary infections which can lead to life-threatening sepsis

Question 29

Toxic epidermis necrolysis (TEN)

Answer 29

Variant of erythema multiforme that is characterized by diffuse necrosis and sloughing of the cutaneous and mucosal epithelial surfaces

Looks very similar to extensive burn victims