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Emergency And Acute Medicine – Angioedema
Core Description
Angioedema is a nonpruritic, well-demarcated, nonpitting swelling of the deeper dermis and subcutaneous tissues caused by increased vascular permeability. It results from inflammatory mediator release, either mast cell mediated or kinin mediated through bradykinin and complement pathways. Unlike urticaria, angioedema affects deeper tissues with fewer mast cells and nerve endings, leading to minimal itching. In addition to the skin, angioedema may involve the gastrointestinal tract and upper airway, and it may occur with or without associated urticaria.
Pathophysiologic Mechanisms
Hereditary and acquired forms of angioedema are related to quantitative or functional deficiencies of C1 esterase inhibitor (C1-INH), resulting in unregulated bradykinin activity. Hereditary angioedema is an autosomal dominant disorder with multiple genetic variants, while acquired forms are associated with lymphoproliferative or autoimmune disease. Angiotensin-converting enzyme inhibitor–related angioedema is common in emergency settings and may occur early or years after initiation of therapy.
Underlying Causes
Kinin-mediated etiologies include hereditary angioedema, acquired C1-INH deficiency, and ACE inhibitor–associated reactions. Mast cell–mediated causes include food allergies, medication reactions, insect stings, and physical triggers such as exercise, temperature changes, or trauma. Idiopathic recurrent angioedema and autoimmune-associated forms are also recognized.
Clinical Features
Patients typically present with sudden, asymmetric swelling of the lips, eyelids, face, tongue, or extremities. Lesions are large, nonpitting, and nonpruritic. Abdominal involvement may cause severe pain, nausea, vomiting, or diarrhea. Airway involvement involving the pharynx or larynx is the most dangerous manifestation and may progress rapidly. Attacks of hereditary angioedema are notably not associated with urticaria or itching.
History And Physical Assessment
A careful history should assess family history, recurrent episodes, recent medication use (especially ACE inhibitors), food exposures, and prior similar events. Emotional stress or minor trauma may precipitate attacks. Physical examination focuses on identifying airway compromise, facial and oropharyngeal swelling, and abdominal tenderness. Lesions typically spare gravity-dependent areas.
Diagnostic Approach
Angioedema is primarily a clinical diagnosis. A family history may be absent, as new mutations account for a significant proportion of hereditary cases. Laboratory testing may support the diagnosis but is not required acutely.
Laboratory And Specialized Testing
Basic studies may include a complete blood count and inflammatory markers. Complement levels such as C4 are often reduced during attacks in hereditary and acquired forms. Measurement of C1-INH levels and function confirms hereditary angioedema but is rarely available in the emergency department. Skin biopsy is rarely required.
Differential Considerations
Conditions that may mimic angioedema include superior vena cava syndrome, heart failure, nephrotic syndrome, facial cellulitis, contact dermatitis, autoimmune connective tissue diseases, hypothyroidism, and facial lymphedema.
Emergency Management Principles
Early airway protection is the priority in all cases. Intravenous access and close monitoring are essential. Epinephrine, antihistamines, and corticosteroids are commonly used when mast cell–mediated angioedema is suspected, though response may be limited in bradykinin-mediated disease. Early intubation should be strongly considered if there is progressive airway involvement.
Targeted Therapy
Hereditary and acquired angioedema may require C1-INH replacement, bradykinin receptor antagonists, or kallikrein inhibitors. Fresh frozen plasma may be used when specific agents are unavailable, though caution is advised. ACE inhibitor–induced angioedema requires immediate discontinuation of the offending drug.
Disposition And Follow-Up
Patients with airway involvement or persistent systemic symptoms require admission and monitored care. Those with mild, nonprogressive symptoms may be discharged after observation with antihistamines, steroids, and clear return precautions. Referral to an allergist or immunologist is recommended for recurrent, hereditary, or unexplained cases.
Clinical Pearls And Pitfalls
Airway compromise can evolve rapidly and unpredictably, necessitating early intervention. Standard allergic therapies may be ineffective in bradykinin-mediated angioedema. Recognition of hereditary angioedema and ACE inhibitor–related cases is critical to avoid delayed or ineffective treatment.
Core Description
Angioedema is a nonpruritic, well-demarcated, nonpitting swelling of the deeper dermis and subcutaneous tissues caused by increased vascular permeability. It results from inflammatory mediator release, either mast cell mediated or kinin mediated through bradykinin and complement pathways. Unlike urticaria, angioedema affects deeper tissues with fewer mast cells and nerve endings, leading to minimal itching. In addition to the skin, angioedema may involve the gastrointestinal tract and upper airway, and it may occur with or without associated urticaria.
Pathophysiologic Mechanisms
Hereditary and acquired forms of angioedema are related to quantitative or functional deficiencies of C1 esterase inhibitor (C1-INH), resulting in unregulated bradykinin activity. Hereditary angioedema is an autosomal dominant disorder with multiple genetic variants, while acquired forms are associated with lymphoproliferative or autoimmune disease. Angiotensin-converting enzyme inhibitor–related angioedema is common in emergency settings and may occur early or years after initiation of therapy.
Underlying Causes
Kinin-mediated etiologies include hereditary angioedema, acquired C1-INH deficiency, and ACE inhibitor–associated reactions. Mast cell–mediated causes include food allergies, medication reactions, insect stings, and physical triggers such as exercise, temperature changes, or trauma. Idiopathic recurrent angioedema and autoimmune-associated forms are also recognized.
Clinical Features
Patients typically present with sudden, asymmetric swelling of the lips, eyelids, face, tongue, or extremities. Lesions are large, nonpitting, and nonpruritic. Abdominal involvement may cause severe pain, nausea, vomiting, or diarrhea. Airway involvement involving the pharynx or larynx is the most dangerous manifestation and may progress rapidly. Attacks of hereditary angioedema are notably not associated with urticaria or itching.
History And Physical Assessment
A careful history should assess family history, recurrent episodes, recent medication use (especially ACE inhibitors), food exposures, and prior similar events. Emotional stress or minor trauma may precipitate attacks. Physical examination focuses on identifying airway compromise, facial and oropharyngeal swelling, and abdominal tenderness. Lesions typically spare gravity-dependent areas.
Diagnostic Approach
Angioedema is primarily a clinical diagnosis. A family history may be absent, as new mutations account for a significant proportion of hereditary cases. Laboratory testing may support the diagnosis but is not required acutely.
Laboratory And Specialized Testing
Basic studies may include a complete blood count and inflammatory markers. Complement levels such as C4 are often reduced during attacks in hereditary and acquired forms. Measurement of C1-INH levels and function confirms hereditary angioedema but is rarely available in the emergency department. Skin biopsy is rarely required.
Differential Considerations
Conditions that may mimic angioedema include superior vena cava syndrome, heart failure, nephrotic syndrome, facial cellulitis, contact dermatitis, autoimmune connective tissue diseases, hypothyroidism, and facial lymphedema.
Emergency Management Principles
Early airway protection is the priority in all cases. Intravenous access and close monitoring are essential. Epinephrine, antihistamines, and corticosteroids are commonly used when mast cell–mediated angioedema is suspected, though response may be limited in bradykinin-mediated disease. Early intubation should be strongly considered if there is progressive airway involvement.
Targeted Therapy
Hereditary and acquired angioedema may require C1-INH replacement, bradykinin receptor antagonists, or kallikrein inhibitors. Fresh frozen plasma may be used when specific agents are unavailable, though caution is advised. ACE inhibitor–induced angioedema requires immediate discontinuation of the offending drug.
Disposition And Follow-Up
Patients with airway involvement or persistent systemic symptoms require admission and monitored care. Those with mild, nonprogressive symptoms may be discharged after observation with antihistamines, steroids, and clear return precautions. Referral to an allergist or immunologist is recommended for recurrent, hereditary, or unexplained cases.
Clinical Pearls And Pitfalls
Airway compromise can evolve rapidly and unpredictably, necessitating early intervention. Standard allergic therapies may be ineffective in bradykinin-mediated angioedema. Recognition of hereditary angioedema and ACE inhibitor–related cases is critical to avoid delayed or ineffective treatment.
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