Allergy
Question 81 of 180
A 54 year old woman presents to the Emergency Department with a 1 hour history of lip and tongue swelling and a urticarial rash after eating a cake. Acute allergic angioedema is mediated by which antibody isotype?
Answer:
Acute allergic angioedema is mediated by IgE causing mast cell degranulation and histamine release.Angioedema
Allergy
Last Updated: 17th June 2020
Definitions
- Urticaria is a superficial swelling of the skin (epidermis and mucous membranes) that results in a red (initially with a pale centre), raised, and intensely itchy rash.
- Angioedema is a deeper form of urticaria with transient swellings of deeper dermal, subcutaneous, and submucosal tissues, often affecting the face (lips, tongue, and eyelids), genitalia, hands, or feet.
- Angioedema most commonly occurs with urticaria but may occur in isolation.
Clinical Features
Angioedema is a deeper form of urticaria with swelling of deeper dermal, subcutaneous, and submucosal tissues, often affecting the face (lips, tongue, and eyelids), genitalia, hands, or feet. Less commonly, submucosal swelling affects the bowel and airway. Bowel wall oedema may cause gastrointestinal symptoms (abdominal pain, nausea, vomiting, abdominal distention, diarrhoea, and/or constipation). Laryngeal involvement can produce stridor and lead to complete airway obstruction.
Classification
- Acute allergic angioedema (90% of cases)
- IgE mediated mast cell degranulation and histamine release as in urticaria
- Almost always occurs with urticaria within 1-2 hours of exposure to the allergen
- Self-limiting in most cases and will resolve in 1–3 days, but relapses are common and unpredictable
- Non-allergic angioedema (bradykinin mediated)
- Drug induced angioedema
- Occurs days to months after taking the eliciting drug, most commonly ACE inhibitors
- The diagnosis is confirmed if symptoms resolve and do not recur after withdrawing the drug
- Episodes may persist for several months after stopping the drug
- Hereditary angioedema (HAE)
- Autosomal dominant genetic abnormality
- C1-esterase-inhibitor deficiency or functional deficiency leading to the overproduction of bradykinin and a increase in vascular permeability
- Usually presents after puberty and is characterised by recurrent oedema of the limbs, trunk, face, and genitals
- Gastrointestinal symptoms are common and can mimic an acute abdomen
- Upper airway swelling is a much less frequent manifestation
- Acquired angioedema (AAE)
- Acquired C1-esterase-inhibitor deficiency, usually secondary to lymphoma or connective tissue disorder e.g. SLE
- The clinical features are similar to those of HAE
- Drug induced angioedema
- Idiopathic angioedema
- Usually a chronic and relapsing angioedema with an unknown cause
- More common in people with autoimmune disorders, such as systemic lupus erythematosus (SLE) and autoimmune thyroiditis
Diagnosis
- For people with angioedema with urticaria:
- Suspect an allergic cause when angioedema is transient (hours or days) and occurs within 1–2 hours of exposure to a known allergen.
- Suspect idiopathic angioedema when the person has recurrent episodes of angioedema and urticaria and an allergic cause cannot be identified.
- For people with angioedema without urticaria, a non-allergic cause is likely:
- Suspect a non-allergic drug reaction if the person is taking an angiotensin-converting enzyme (ACE) inhibitor.
- Suspect hereditary angioedema (HAE) if there is a history of one of the parents being affected.
- Suspect acquired angioedema (AAE) if the person is known to have lymphoma or a connective tissue disorder and no family history of angioedema.
| Allergic Angioedema | Non-Allergic Angioedema | Anaphylaxis |
|---|---|---|
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Differential Diagnosis
- Evolving anaphylaxis
- Cellulitis
- Erysipelas
- Lymphoedema
- SLE
- Contact dermatitis
Management in ED
Assessment of potentially life-threatening conditions should follow a structured ABC pattern. If an evolving anaphylactic reaction is suspected then treatment should follow that of anaphylaxis.
- Allergic angioedema:
- For people with rapidly developing angioedema (without anaphylaxis):
- Give slow intravenous (IV) or intramuscular (IM) chlorphenamine and hydrocortisone
- Arrange emergency admission
- Arrange a review after the person has been discharged from hospital
- For people with stable angioedema:
- Try to identify the underlying cause so that further episodes can be avoided
- For people with mild symptoms of angioedema, treatment may not be needed
- For people with symptoms requiring treatment:
- Offer a non-sedating antihistamine (such as cetirizine, fexofenadine, or loratadine) for up to 6 weeks (use clinical judgement to determine the duration of treatment)
- If symptoms are severe, give a short course of an oral corticosteroid (for example prednisolone 40 mg daily for up to 7 days) in addition to the non-sedating oral antihistamine
- Advise the person to seek immediate medical help (by dialling 999 or attending A&E) if symptoms progress rapidly or if symptoms of anaphylaxis develop.
- For people with rapidly developing angioedema (without anaphylaxis):
- Hereditary Angioedema (suspect if there is a history of one of the parents being affected):
- As angioedema associated with C1 esterase inhibitor deficiency is modulated by bradykinin it requires an alternative management strategy. It often does not respond to treatment with adrenaline, antihistamines and corticosteroids. Attacks of HAE should be treated with Icatibant (a bradykinin B2 receptor antagonist) or C1 esterase inhibitor concentrate (if available). C1 esterase inhibitor is also found in fresh frozen plasma and two units are effective in abolishing an attack. Icatibant is administered as a single subcutaneous injection and has been shown to start producing symptomatic improvement in under an hour. C1 esterase inhibitor concentrate and FFP are derived from donated blood and require intravenous administration.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
