Dermatitis

Question 1

What are the two types of contact dermatitis and are they mutually exclusive?

Answer 1

1. Allergic contact dermatitis - allergic response caused by contact with a substance
2. Irritant contact dermatitis -irritation to the skin by contact with a chemical or physical irritant

Not mutually exclusive -> processes can occur simultaneously in some patients

Question 2

What type of reaction is an allergic contact dermatitis (ACD) and what are the two phases?

Answer 2

Cell mediated, delayed type IV hypersensitivity reaction

1. Sensitization phase - allergen penetrates epidermis, presented by Langerhaans cells to T-cells, takes 1-14 days
2. Elicitation phase - re-exposure to allergen activates T-cell response in hours to day

Question 3

How long can ACD persist after antigen removal? How is it diagnosed?

Answer 3

Up to 3 weeks after removal of agent

Diagnosed via patch testing to identify allergen

Question 4

What are common allergens which are associated with the Type IV hypersensitivity of ACD?

Answer 4

1. Urushiol (poison ivy)
2. Nickel jewelry
3. Neomycin / bacitracin
4. Black hair dye

Question 5

What does ACD look like acutely and chronically?

Answer 5

Acutely - bright red / erythematous

Chronically - xerotic, fissured, lichenified eczematous plaques

Question 6

In addition to the common allergens for ACD, what are some common causes which can lead to ACD on the eyelids?

Answer 6

1. Cosmetics
2. Nickel eyelash curlers
3. Antibiotic eyedrops
4. Nailpolish removers
5. Eyelash adhesives
6. Hair dyes

Question 7

How is ACD treated? How long does it take before skin barrier function has normalized?

Answer 7

1. Exposure avoidance
2. Topical corticosteroids
3. If severe, oral corticosteroids with at LEAST 14 day taper (prevent rebound symptoms)
4. Emollients / moisturizers since barrier function takes 4 months to normalize

Question 8

What is the most common form of contact dermatitis?

Answer 8

Irritant contact dermatitis (ICD). It is also the majority of occupational dermatitis

Question 9

What causes ICD?

Answer 9

Non-immunologic response to chemical / physical agents, i.e.:

Soap, industrial cleansers, frictional forces
-> risk factors are occupations with repeated exposures to water, soaps, and solvents

Question 10

How does acute ICD appear? Common locations?

Answer 10

Usually well demarcated (borders of where irritant touched) erythematous and scaly patches and plaques

Severe disease can develop vesicles and bullae

Common locations: Hands, forearms, eyelids, face

Question 11

How does chronic ICD appear? Who would tend to get it?

Answer 11

Less erythematous, more lichenified than acute ICD. Often fissuring, scaling, and hyperkeratosis

Tends to occur with chronic exposures to solvents -> i.e. housewives

Question 12

How is ICD managed?

Answer 12

Using more gloves, reducing exposure as much as possible, watching hands in cool / tepid water rather than hot which strips oil out of hands, topical steroids if needed.

Question 13

What is eczema also called? What other conditions are associated with it?

Answer 13

Atopic dermatitis

Tends to happen in people who have a FHx of:

1. Asthma
2. Hay fever
3. Eczema

Occurs in industrialized urban areas more

Question 14

What gene is commonly mutated in patients with eczema, and what are they at increased risk for?

Answer 14

Filaggrin, a gene required for proper barrier function of the skin

Increased infection risk due to lack of proper barrier function
-> S. aureus, molluscum, HSV, HPV

Question 15

What antibody tends to be elevated in atopic dermatitis, and do elimination diets tend to help?

Answer 15

IgE antibodies are high since it is associated with other IgE-related conditions, and eczema is thought to be partially Type 1 hypersensitivty

Dietary modifications do not help

Question 16

What is the morphology of the rash in atopic dermatitis? Include chronic changes.

Answer 16

Red, crusted, scaly, pruritic plaques with vesicles and edema

If chronic: Lichenification and hyperpigmentation

Question 17

Where does eczema appear in infants vs children / adults?

Answer 17

Infants - Face (esp. cheeks) and extensor surfaces since they are always lying on their back

Children / adults - Flexor extremities (antecubital and popliteal fossae), wrists, ankles

Question 18

What is one big way to tell eczema apart from candidiasis or Letterer-Siwe (Langerhans cell histiocytosis)?

Answer 18

In eczema, the diaper area is spared.

It is heavily involved in these two conditions.

Question 19

How does eczema look in skin of dark-skinned people?

Answer 19

Often appears brown or purple, with erythema apprecitated at periphery

Can leave post-inflammatory hyperpigmentation

Question 20

What are possible simple or OTC options for treatment of eczema?

Answer 20

Avoiding triggers: i.e. dust mites and pollen

Repair skin barrier: moisturizers and lukewarm baths

Treatment of secondary infections with bleach bath

Antihistamines may have some utility

Question 21

What are some prescription options for the treatment of eczema? Side effects?

Answer 21

1. Topical steroids (ointments most potent) -> cutaneous atrophy
2. Topical calcineurin inhibitors - pimecrolimus / tacrolimus -> black box warning of lymphoma
3. Systemic steroids -> have high rate of relapse
4. Phototherapy + systemic immunosuppressives -> UVA, narrow band UVB, MTX, AZA to calm immune response

Question 22

What are serious infections which can arise in the setting of atopic dermatitis and how are they avoided / treated?

Answer 22

Staphylococcal - avoid with bleach paths, treat with antibiotics

VZV, HSV - Eczema herpeticum, treat with antivirals, but can be a dermatologic emergency requiring IV rehydration and antivirals

Question 23

What disease is characterized by coin-shaped, scaly red/brown pruritis plaques with NO central clearing? What symptoms will the patient show?

Answer 23

Nummular dermatitis

Patient shows severe pruritis -> scratching often becomes habitual

Question 24

Who tends to get nummular dermatitis and when is it thought to be worse? What is the treatment?

Answer 24

Tends to be in middle-aged and elderly. Disease is worse in the winter, due to impaired skin barrier function

Treatment is high dose steroids and moisturization

Question 25

What is dyshidrotic dermatitis? How do the lesions appear?

Answer 25

Pruritic vesicular skin disorder of palms and soles, has nothing to do with sweat glands. Lesions are very small and "tapioca-like" vesicles with minimal erythema. Typically occurs on lateral fingers.

Question 26

What lab should you run for dyshidrotic dermatitis and nummular dermatitis?

Answer 26

KOH prep to ensure absence of dermatophytes

Question 27

How does Lichen Simplex Chronicus (LSC) develop?

Answer 27

Occurs due to chronic rubbing / scratching of skin -> often seen in patients with chronic, pruritic skin disease like atopic dermatitis, or systemic pruritis (end stage renal disease or liver disease (jaundice))

Question 28

What does Lichen Simplex Chronicus look like? Where is it commonly found?

Answer 28

Lichenified, often hyper-pigmented plaques Trunk, extremities, and scrotum is very common

Question 29

What is the treatment for LSC?

Answer 29

Super potent steroid ointments, oral antihistamines (reduce itch), antidepressants if there is any psychological component to the itching. Also help the patient identify habitual nature of itching and try to replace the compulsion with something else.

Question 30

What is the cause of prurigo nodularis? What is the treatment?

Answer 30

Condition extremely similar to LSC, except it is due to chronic rubbing & picking -> Treatment is exactly the same as LSC

Question 31

What do lesions in prurigo nodularis look like?

Answer 31

Lichenified, hyperpigmented PAPULES and small plaques -> lesions tend to be more nodular than LSC, and are more caused by picking than itching