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Yr 3 - Core Conditions > Dermatology - Cutaneous Drug Eruptions > Flashcards

Dermatology - Cutaneous Drug Eruptions Flashcards

1
Q

What is a pseudoallergy?

A

Pseudo-allergic are defined as those reactions that produce the same clinical symptoms with anaphylaxis but are not IgE mediated.

E.g. . opiates increase histamine release, causing urticaria

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2
Q

What 4 drugs commonly cause allergic reactions? (4 A’s)

A
  • Antibiotics → penicillins, cephalosporins, co-trimoxazole
  • Anti-epileptics → phenytoin, carbamazepine
  • Anti-inflammatories → NSAIDs
  • Allopurinol
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3
Q

What is the most common type of drug rash?

A

Morbilliform eruption (95%)

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4
Q

What type of rash is characteristic of a morbilliform eruption?

A

Generalised maculopapular rash

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5
Q

What are morbilliform eruptions common complications of?

A

medications

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6
Q

What type of reaction is a morbilliform eruption?

A

Type IV T cell mediated hypersensitivity reaction

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7
Q

Time between exposure to drug and morbilliform eruption?

A

Delay of 1-2 weeks between starting the drug and the rash. However, on re-exposure, the rash can appear much faster.

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8
Q

In children, what is a major differential for a morbilliform eruption?

A

In children, a similar rash is usually indicative of a viral exanthem/rash (or measles in an unvaccinated child).

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9
Q

Give some pharmacological causes of a morbilliform eruption

A
  • Amoxicillin – especially if the patient is also infected with EBV (glandular fever)
  • Beta-lactam antibiotics
  • Sulfonamides
  • Allopurinol
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10
Q

What type of drug eruption is caused by giving amoxicillin to a patient with EBV?

A

Morbilliform

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11
Q

Is the patient typically systemically unwell in a morbilliform eruption?

A

No

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12
Q

Main complications of a morbilliform eruption?

A

Can progress to erythroderma, SJS/TEN!

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13
Q

What type of rash characterises uritcaria?

A

Characterised by itchy, red wheals (hives)** with **angioedema (swelling of the subcutaneous tissue). A wheal can last a few minutes and can change form.

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14
Q

What type of reaction is urticaria?

A

Type I IgE mediated hypersensitivity reaction

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15
Q

Time between exposure to drug and urticaria?

A

occurs very rapidly after taking the drug (<2 hours).

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16
Q

Common causes of urticaria

A
  • Idiopathic
  • NSAIDs
  • Beta-lactam antibiotics
  • Opiates
  • ACEi
  • Aspirin
  • Radio contrast agents
  • Food allergy
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17
Q

What type of reaction is seen in anaphylaxis?

A

Type I - urticaria & angiodema

18
Q

Describe a wheal

A

Raised plaques with erythematous edges with central clearing

19
Q

Diagnostic investigation of urticaria?

A

Skin prick test

20
Q

Management of urticaria?

A

Antihistamine

21
Q

What is a fixed drug eruption?

A

Characterised by circular, erythematous patches** that may contain a blister that recur in the **same location every time the drug is taken (localised rash).

22
Q

Onset of a fixed drug eruption?

A

Onset usually within hours.

23
Q

How does a fixed drug eruption change with repeat exposure?

A

May become more severe or widespread with repeat exposure

24
Q

Give some pharmacological causes of a fixed drug eruption

A
  • Paracetamol
  • Sulfonamides
  • Tetracycline antibiotics
  • NSAIDs
25
Q

Presentation of a fixed drug eruption rash?

A
  • Usually localised rash
  • Circular, erythematous patches that may contain a blister
  • Same site each time drug is taken
  • Location → hands, feet, lips, eye lids, genitals
26
Q

What is a serious cutaneous adverse reaction (SCAR)?

A

A group of potentially lethal adverse drug reactions that involve the skin and mucous membranes of various body openings such as the eyes, ears, and inside the nose, mouth, and lips. In more severe cases, SCARs also involves serious damage to internal organs.

27
Q

Give some examples of Serious Cutaneous Adverse Reactions (SCAR)

A
  1. Drug reaction with eosinophilia and systemic symptoms (DRESS) / Drug hypersensitivity syndrome (DHS)
  2. Acute exlanthematous generalised pustulosis (AGEP)
  3. Steven Johnson Syndrome (SJS) + Toxic epidermal necrolysis (TEN)
28
Q

What is DRESS/DHS?

A

A specific, severe, unexpected reaction to a medicine, which affects several organ systems at the same time.

Classified as a SCAR.

29
Q

Onset of DRESS/DHS?

A

Occurs 2-8 weeks after starting a drug

30
Q

Presentation of DRESS/DHS?

A
  • Rash – similar to morbilliform eruption
    • Can develop erythroderma
  • Fever
  • Lymphadenopathy (75% of cases )
  • Facial swelling
  • Haematological abnormalities
  • Inflammation of internal organs
  • Mucous ulceration (mouth, eyes, genitals)
31
Q

What may a FBC show in DRESS/DHS?

A
  • Raised WCC - particularly eosinophils
  • May develop anaemia - low Hb
  • May develop low platelets (thrombocytopenia)
32
Q

What may LFTs show in DRESS/DHS?

A

can cause hepatitis (deranged LFTs in 80%)

33
Q

What may U&Es show in DRESS/DHS?

A

can cause nephritis

34
Q

Mortality rate of DRESS/DHS?

A

8% mortality due to fulminant hepatitis, multi-organ failure

35
Q

What is Acute Exlanthematous Generalised Pustulosis (AGEP)?

A

An uncommon pustular drug eruption characterised by superficial pustules.

Classified as a SCAR to a prescribed drug.

36
Q

Onset of AGEP?

A

Within 2 days of starting drug.

37
Q

Presentation of AGEP?

A
  • May start axillae/groins/face then becomes generalised
  • Erythroderma with sheets of small pustules (characteristic)
  • Oral lesions
  • Fever and malaise but generally not unwell (10% organ dysfunction)
38
Q

FBC in AGEP?

A

Bloods show neutrophilia (instead of eosinophils seen in DRESS).

39
Q

FBC results in DRESS vs AGEP?

A

AGEP → neutrophils raised

DRESS → eosinophils raised

40
Q

What is the most common cause of a morbilliform eruption?

A

Oral Abx

Yr 3 - Core Conditions (33 decks)

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