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Y2 Dermatology > Week 1.5 > Flashcards

Week 1.5 Flashcards

1
Q

What are the 2 stages in all hypersensitivity reactions

A

Sensitisation stage
Effector stage

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2
Q

Features of type 1 hypersensitivity reaction

A

Immediate reaction - symptoms onset minutes up to Hours
IgE mediated

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3
Q

Mechanism of type 1 hypersensitivity reaction

A
  1. On first exposure to allergen, B cells produce IgE antibodies
  2. Some remaining IgE antibodies bind to Fc receptors of mast cells
  3. Mast cells circulate the blood stream
  4. On re-exposure to the allergen, the antigen binds onto IgE on mast cells causing mast cells to degranulate
  5. Mast cells release histamine and inflammatory cytokines
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4
Q

Common allergens causing type 1 hypersensitivity

A

Pollen
Food
Animals
Drugs

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5
Q

Symptoms that can be caused by type 1 hypersensitivity

A

Urticaria - very itchy lesions that look like hives
Angioedema
Anaphylaxis (if severe reaction)
Asthma

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6
Q

Symptoms of anaphylaxis

A

Laryngeal / pharyngeal oedema
Bronchospasm
tachypnea
Hypotension
Tachycardia
Urticaria
Allergic rhinitis / conjunctivitis

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7
Q

Investigations for type 1 hypersensitivity

A

History
Skin prick test
Challenge test if skin prick test is negative but history strongly suggests so

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8
Q

First line treatment for type 1 hypersensitivity

A

Avoid allergen

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9
Q

Management for acute T1 hypersensitivity attack

A
  1. Anti-histamines
  2. Corticosteroids
  3. Epi pen (adrenaline pen) if anaphylaxis
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10
Q

Examples of anti-histamines

A

Chlorphenamine
Diphenhydramine

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11
Q

Examples of corticosteroids used in type 1 hypersensitivity

A

Prednisolone

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12
Q

Features of type 2 hypersensitivity

A

Takes hours - days for reaction after exposure
IgG and IgM mediated
Cytotoxic reaction

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13
Q

How does IgG and IgM cause cytotoxic reaction in type 2 hypersensitivity

A

Activation of complement system
Antibody dependent cell mediated cytotoxicity (ADCC)
Opsonization

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14
Q

Describe the antibody-dependent cell mediated cytotoxicity in type 2 hypersensitivity

A
  1. IgG/IgM binds to antigens
    2 Natural killer cells bind to the Fc portion of IgM/IgG antigen complexes
  2. NK cells causes cell death
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15
Q

Examples of conditions due to Type 2 hypersensitivity

A

Haemolytic anaemia
Goodpasture’s syndrome
Grave’s disease
Bullous pemphigoid

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16
Q

What is Goodpasture’s syndrome

A

When the IgG and IgM antibodies are directed to attack a specific collagen found in basement membrane of alveoli and glomeruli
Causes lungs and kidney damage

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17
Q

Presentation of Goodpasture’s syndrome

A

Haemoptysis
SOB
Renal dysfunction - decreased urine output
Renal failure

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18
Q

Features of type 3 hypersensitivity

A

Takes hours - days for reaction to occur after exposure
Antigen-antibody immune complex mediated

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19
Q

Difference between type 2 and type 3 hypersensitivity

A

In type 3, the antibodies are bound to soluble antigens unlike in type 2 where IgG and IgM are bound to antigens on cells
In type 3, it triggers inflammation cascade in certain areas instead of cytotoxicity in type 2

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20
Q

Mechanism of type 3 hypersensitivity

A
  1. sensitisation
  2. effector stage: Antibody covers the soluble antigen forming antibody-antigen complexes. The complexes can move and deposit in certain areas and trigger inflammation there
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21
Q

The immune complexes in type 3 hypersensitivity often deposit in

A

Blood vessels
Synovial joints
Glomerular basement membrane

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22
Q

Examples of conditions due to type 3 hypersensitivity

A

Rheumatoid arthritis
SLE
Post streptococcal glomerulonephritis

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23
Q

Features of type 4 hypersensitivity

A

Takes days for reaction to occur after exposure
T cell mediated

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24
Q

Why is type 4 hypersensitivity called delayed hypersensitivity

A

Because it takes time for T cells to recruit to sites where antigen is at hence causes delayed response

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25
Q

Examples of conditions due to type 4 hypersensitivity

A

Contact dermatitis
Drug eruptions - exanthematous and fixed drug eruptions

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26
Q

What are drug eruptions

A

Symmetrical skin eruption due to certain medications and this skin eruption resolves after withdrawal of the medication

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27
Q

The amount of time drug eruptions take to resolve depends on

A

the half life of the drug

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28
Q

Different types of drug eruptions (depending on presentation)

A

Exanthematous drug eruption
Urticarial drug eruption
Bullous or pustular drug eruption
Fixed drug eruption

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29
Q

Risk factors for drug eruptions

A

Elderly, young adults
Females
Genetics
HIV / EBV / CMV / cystic fibrosis
Drugs that have higher risk of causing drug eruptions

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30
Q

What are the drugs that have higher risk of causing drug eruptions

A

Beta lactam antibiotics
NSAID
Anti-epilepsy drugs
Topical drugs

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31
Q

Which type of drug eruption is the most common

A

Exanthematous drug eruption

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32
Q

Exanthematous drug eruption is due to which type of hypersensitivity

A

Type 4

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33
Q

Onset of symptoms of exanthematous drug eruptions

A

4 - 21 days

May appear within 1-3 days on re-exposure to the drug

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34
Q

What are the drugs that commonly causes exanthematous drug eruption

A

Penicillin (beta lactam antibiotics)
Carbamezapine and phenytoin
Allopurinol
Erythromycin
Streptomycin
NSAID

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35
Q

What type of drugs are carbamezapine and phenytoin

A

Anti-epileptic drugs

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36
Q

What is allopurinol used for

A

To treat gout attacks

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37
Q

Symptoms of mild - moderate exanthematous drug eruption

A

Widespread bilateral symmetrical macules and papule
Pruritus
Mild fever

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38
Q

Which parts of the body is often spared in exathematous drug eruption

A

Mucous membranes
Axilla
groin
hands
feet

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39
Q

What are the symptoms of severe exanthematous drug eruption

A

High fever
Involvement of mucous membranes
Widespread oedema and erythema
Blisters / necrosis
Skin pain
Dyspnea

40
Q

Which type of hypersensitivity causes urticarial drug eruptions

A

Type 1

41
Q

Urticarial drug eruptions can occur on first exposure as well. Why

A

Due to pseudo-allergic reaction which is not dependent on the immune system (not IgE dependent)

42
Q

What is pseudo allergic reaction

A

When it causes direct release of histamine and cytokines from mast cells without needing IgE to bind to Fc receptors of mast cells first

43
Q

Onset of symptoms in urticarial drug eruptions due to type 1 hypersensitivity

A

Immediate reaction

44
Q

Drugs that causes urticarial reaction due to type 1 hypersensitivity

A

Beta lactam antibiotics
Carbamezapine, phenytoin (anti-epileptics

45
Q

Examples of beta lactam antibiotics

A

Penicillins - amoxicillin, penicillin
Cephalosporin - cephalexin, ceftriazone

46
Q

Drugs that can cause urticarial reaction due to pseudo allergic reaction

A

Opiates
NSAID
Aspirin
Vancomycin

47
Q

Symptoms of urticarial drug eruptions

A

Pruritic red hives rash
Angio-oedema

48
Q

What are the subtypes of bullous / pustular drug eruptions

A

Acneiform
Acute generalised exanthematous pustulosis
Drug induced bullous pemphigoid
Linear IgA disease

49
Q

What is Acneiform

A

Pus filled, red, acne like bumps but are not acne

50
Q

How to differentiate between acneiform drug eruption and acne

A

Acneiform resolves with discontinuation of drug
Acneiform has an acute onset

51
Q

Drugs that causes aceniform eruption

A

Steroids
Androgens
Lithium
Isoniazid

52
Q

What is isoniazid used for

A

treat TB

53
Q

Onset of symptoms for acute generalised exanthematous pustulosis is

A

within 2 days of exposure

54
Q

Drugs that causes acute generalised exanthematous pustulosis

A

Beta lactam antibiotics
CCB
Tetracyclines
Hydroxycloroquine
Carbamazepine
Paracetamol

55
Q

What is hydroxycloroquine used for

A

It is a DMARD, used for rheumatoid arthritis
It is also used to treat malaria

56
Q

Symptoms of acute generalised exanthematous pustulosis

A

Widespread rash
Many small, non-follicular, sterile pustules

57
Q

What are non-follicular pustules

A

The inflammatory infiltrate does not accumulate in hair follicles

58
Q

What is a sterile pustule

A

Bacterial culture obtained from the pustular fluids is negative

59
Q

Symptoms of drug induced bullous pemphigoid

A

Itchy large bullae
Eruptions of bullae causes crusted erosions

60
Q

Drugs that causes drug induced bullous pemphigoid

A

PD1 inhibitor immunotherapies
ACEi
Penicillin
Furosemide
DPP4

61
Q

What is linear IgA disease

A

Linear deposits of IgA at basement membrane causing bullae

62
Q

Which drug can trigger linear IgA disease

A

Vancomycin

63
Q

What is fixed drug eruption

A

Reaction that recurs at the same site on re-exposure to the medication

64
Q

Which type of hypersensitivity causes fixed drug eruption

A

Type 4

65
Q

What drugs causes fixed drug eruption

A

NSAID
Paracetamol
Tetracycline
Sulfonamides

66
Q

Type of rash caused by fixed drug eruption

A

Well demarcated round plaques
Red
Painful
Persistent pigmentation even after stopping the drug
May occur as bullous / on mucous membranes

67
Q

Which mucous membranes can be affected by fixed drug eruption

A

Lips
Tongue
Genitals

68
Q

What is Stevens-Johnson Syndrome (SJS)

A

Dermatological emergency most commonly caused by severe drug reactions but can also be caused by viral infections

69
Q

What is Toxic epidermal necrolysis

A

The most severe form of Stevens-Johnson Syndrome

70
Q

Drugs that can cause SJS

A

Sulfonamides
Beta lactam antibiotics
NSAID
Anti-epileptics - carbamezapine and phenytoin
Allopurinol

71
Q

Viral infections that can cause SJS

A

Herpes Simplex
EBV
HIV
Influenza
Hepatitis

72
Q

When do symptoms of SJS usually present

A

within a week of taking a medication

73
Q

Symptoms of SJS

A

Mucosal ulceration of at least 2 mucosal membranes
Erythematous macules that become target shaped
Flaccid blisters
Systemically unwell

74
Q

What are the mucosal membranes that can be affected by SJS

A

Mouth
Conjunctiva
Urethra
Pharynx
GI tract

75
Q

What is a target lesion

A

Round lesion with 3 colour zones:
- darker center
- raised pale pink ring around the center
- bright red outermost ring

76
Q

Investigations for SJS

A

Nikolsky sign
Skin biopsy

77
Q

What is Nikolsky sign

A

When slightly rubbing the roof of the lesion using eraser part of the pencil causes the lesion to open

78
Q

How does SJS lead to death

A

Due to damage to the skin barrier = the skin loses its function
- dehydration
- infection
- hypothermia
- disseminated intravascular coagulation

79
Q

What is disseminated intravascular coagulation

A

Coagulation pathway becomes overreactive causing formation of blood clots

80
Q

Management of SJS

A

Supportive - pain relief, antibiotics if there is infection
Ophthalmology referral

81
Q

What is drug phototoxicity

A

Non-immunological skin reaction due to light activation of a photo-reactive drug

82
Q

Which UV light most commonly causes drug phototoxicity

A

UVA

83
Q

Common phototoxic drugs

A

NSAID
CCB
Thiazide diuretics
Amiodarone
Tetracycline
Quinine
Chlorpromazine

84
Q

What is quinine used for

A

Malaria
Leg cramps

85
Q

What is chlorpromazine used for

A

Psychosis, anxiety, mania

86
Q

What are the skin reactions due to phototoxicity

A

Exaggerated sunburn
Pseudoporphyria
Exposed telangiectasia
Delayed erythema and pigmentation
Immediate prickling with delayed erythema and pigmentation

87
Q

What is psuedoporphyria

A

Bullous photodermatosis with features of porphyria cutanea tarda but without any abnormalities in porphyrin metabolism

88
Q

What is porphyrin cutanea tarda

A

Painful blisters that develop when you become exposed to the sun

89
Q

What causes porphyrin cutanea tarda

A

Deficiency in UROD enzyme (uroporphyrinogen decarboxylase) which is needed to break down porphyrin.
Build up of porphyrin causes porphyrin to absorb sunlight and become activated and causes damage to skin

90
Q

Which drugs cause exaggerated sunburn due to phototoxicity

A

Thiazides
Quinine
Tetracycline

91
Q

Which drug causes pseudoporphyria due to phototoxicity

A

NSAID

92
Q

Which drug causes telangiectasia on sun exposed sites due to phototoxicity

A

CCB

93
Q

Which drugs cause delayed erythema and pigmentation due to phototoxicity

A

Psoralen

94
Q

When is psoralen used

A

PUVA (phototherapy) for psoriasis

95
Q

Which drug causes immediate prickling with delayed erythema and pigmentation due to phototoxicity

A

Amiodarone
Chlorpromazine

96
Q

Management of phototoxicity

A

Discontinue the drug and use alternative
Topical steroids

Y2 Dermatology (5 decks)

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