Dermatitis

Question 1

What are the two main types of contact dermatitis?

Answer 1

irritant
allergic

Question 2

What usually causes irritant contact dermatitis?

Answer 2

• common non-allergic reaction - due to weak acids or alkalis (e.g. detergents).

Question 3

What is the cause of allergic contact dermatitis?

Answer 3

• Type IV hypersensitivity reaction.
• often seen on the head following hair dyes.
• Nickel Allergy

Question 4

Where does irritant contact dermatitis normally present?

Answer 4

Hands

Question 5

Main feature of irritant contact dermatitis?

Answer 5

Erythema
(crusting and vesicles are rare)

Question 6

How does an allergic contact dermatitis normally present?

Answer 6

• Acute weeping eczema

Question 7

Treatment of allergic contact dermatitis?

Answer 7

Topical potent steroids

Question 8

Give an example of something which can cause both contact and irritant dermatitis?

Answer 8

Cement
- The alkaline may cause an irritant contact dermatitis
- the dichromates cause an allergic reaction

Question 9

What is dermatitis artfacta?

Answer 9

psycho-dermatological condition characterised by self-inflicted skin lesions

Question 10

Who normally presents with dermatitis artefacta?

Answer 10

Adolescent females
- strongly associated with personality disorder, dissociative disorders and eating disorders

Question 11

Features of dermatitis artefacta

Answer 11

• linear/geometric lesions, well-demarcated from normal skin
• skin lesions “appear suddenly” e.g. overnight
• the lesions do not evolve over time
• multiple lesions at various stages of healing
• face (especially cheeks) and the dorsum of the hands most common

Question 12

Mechanism of injuries in dermatitis artefacta

Answer 12

• scratching with fingernails or other objects
• burning skin with cigarettes
  or chemicals (deodorant spray)

Question 13

Management of dermatitis artefacta

Answer 13

• co-managed by dermatologists, psychologists and psychiatrists
• occlusive dressing
• topical antibiotics (if necessary) - bland emollient
• SSRI and CBT may be helpful

Question 14

Dermatitis herpetiformis is associated with which other autoimmune disease?

Answer 14

coeliac

Question 15

What autoimmune phenomenon causes dermatitis herpetiformis?

Answer 15

deposition of IgA in the dermis.

Question 16

Describe the features of dermatitis herpetiformis

Answer 16

itchy, vesicular skin lesions on the extensor surfaces
(e.g. elbows, knees, buttocks)

Question 17

What investigation would help diagnose dermatitis herpetiformis?

Answer 17

• skin biopsy
• direct immunofluorescence shows deposition of IgA in a granular pattern in the upper dermis

Question 18

Management of dermatitis herpetiformis

Answer 18

• gluten-free diet
• dapsone

Question 19

What is seborrhoeic dermatitis caused by?

Answer 19

• inflammatory reaction to Malassezia furfur
• normal fungal skin inhabitant

Question 20

Features of seborrhoeic dermatitis

Answer 20

Eczematous lesions on the sebum-rich areas
> scalp (may cause dandruff)
> periorbital, auricular and nasolabial folds
> otitis externa and blepharitis

Question 21

What conditions are associated with seborrhoeic dermatitis?

Answer 21

Parkinson’s Disease
HIV

Question 22

Management of Seborrhoeic dermatitis on the scalpe

Answer 22

• OTC containing zinc pyrithione and tar
• 2nd-line agent is ketoconazole
• selenium sulphide and topical corticosteroid

Question 23

Management of seborrhoeic dermatitis on the body

Answer 23

• topical antifungals: e.g. ketoconazole
• topical steroids: best used for short periods