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In medicine and immunology, angioedema is type of hypersensitivity that is a "swelling involving the deep dermis, subcutaneous, or submucosal tissues, representing localized edema. Angioedema often occurs in the face, lips, tongue, and larynx."[1] Angioedema of sudden onset, as in anaphylaxis, can be a life-threatening respiratory emergency.


Among patients with recurrent angioedema without urticaria, 38% are idiopathic, 25% are due to deficiency of functional complement C1 inhibitor protein (C1 esterase inhibitor), 16% are related to an environmental exposure (medication, foodstuff, insect bite, other environmental allergen, or physical irritation), and 11% are due to angiotensin-converting enzyme inhibitor treatment.[2]

C1 esterase inhibitor deficiency

Angioedema due to deficiency of functional complement C1 inhibitor protein manifest by edema without urticaria, without pruritis[3][4][5] and may be reduced have reduced d-dimer levels, especially during attacks.[6]

Hereditary angioedema (Hereditary C1 esterase inhibitor deficiency)

For more information, see: Hereditary angioedema.

Hereditary deficiency is characterized by normal levels of complement C1q and complement C1 inhibitor protein function.[5] Complement C1 inhibitor protein antigen is low in type I and normal in type II.

Acquired angioedema (Acquired C1 esterase inhibitor deficiency)

Acquired C1 esterase inhibitor deficiency is rare.[4][5]

  • Type I disease is associated with lymphoproliferative disorders.[5]
  • Type II disease is associated with autoantibodies[5] and monoclonal gammopathies[7].

Acquired deficiency is characterized by low levels of complement C1q.[5] Like hereditary angioedema, it has low complement C1 inhibitor protein function.[5] Complement C1 inhibitor protein antigen is low in type I and normal in type II. It also has decreased complement C4[8] unless a paraprotein is present[9].

Treatment includes oral tranexamic acid oral 1 gram 3 times a day. Tranexamic acid is an "inhibitor of plasminogen activation, and at much higher concentrations, a noncompetitive inhibitor of plasmin, i.e., actions similar to aminocaproic acid." It is similar to, but more potent than aminocaproic acid.[10] Concomittent use of warfarin may be needed to prevent embolism and thrombosis.

Insect bite

Angioedema may be due to insect bites.[11]

The risk of subsequent systemic anaphylaxis is 5% to 15% according to a review[11] that cites several case series.[12][13][14][15][16] This risk may be increased in patients with a positive skin test[13] or elevated IgE to bee venom.[17]

Immunotherapy may reduce the size and duration of subsequent episodes.[18]


Protecting the airway is of first importance. If there is any significant compromise, admit the patient to an intensive care unit; otherwise observe in an emergency room. Discontinue all potentially causative drugs.

Provide supplemental oxygen and monitor oxygenation. If the airway is compromised, protect it with appropriate intubation or other intubation, and administer 1:1000 epinephrine subcutaneously or intramuscularly every 10 minutes.

Give antihistamines and corticosteroids.[19]


  1. Anonymous (2023), Angioedema (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. Zingale LC, Beltrami L, Zanichelli A, et al (October 2006). "Angioedema without urticaria: a large clinical survey". CMAJ 175 (9): 1065–70. DOI:10.1503/cmaj.060535. PMID 17060655. PMC 1609157. Research Blogging.
  3. Agostoni A, Aygören-Pürsün E, Binkley KE, et al (September 2004). "Hereditary and acquired angioedema: problems and progress: proceedings of the third C1 esterase inhibitor deficiency workshop and beyond". J. Allergy Clin. Immunol. 114 (3 Suppl): S51–131. DOI:10.1016/j.jaci.2004.06.047. PMID 15356535. Research Blogging.
  4. 4.0 4.1 Cicardi M, Zingale LC, Pappalardo E, Folcioni A, Agostoni A (July 2003). "Autoantibodies and lymphoproliferative diseases in acquired C1-inhibitor deficiencies". Medicine (Baltimore) 82 (4): 274–81. DOI:10.1097/ PMID 12861105. Research Blogging.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Markovic SN, Inwards DJ, Frigas EA, Phyliky RP (January 2000). "Acquired C1 esterase inhibitor deficiency". Ann. Intern. Med. 132 (2): 144–50. PMID 10644276[e]
  6. Cugno M, Zanichelli A, Bellatorre AG, Griffini S, Cicardi M (February 2009). "Plasma biomarkers of acute attacks in patients with angioedema due to C1-inhibitor deficiency". Allergy 64 (2): 254–7. DOI:10.1111/j.1398-9995.2008.01859.x. PMID 19076541. Research Blogging.
  7. Frémeaux-Bacchi V, Guinnepain MT, Cacoub P, et al (August 2002). "Prevalence of monoclonal gammopathy in patients presenting with acquired angioedema type 2". Am. J. Med. 113 (3): 194–9. PMID 12208377[e]
  8. Gompels MM, Lock RJ, Morgan JE, Osborne J, Brown A, Virgo PF (February 2002). "A multicentre evaluation of the diagnostic efficiency of serological investigations for C1 inhibitor deficiency". J. Clin. Pathol. 55 (2): 145–7. PMID 11865013. PMC 1769585[e]
  9. McLean-Tooke A, Stroud C, Sampson A, Spickett G (May 2007). "Falsely normal C4 in a case of acquired C1 esterase inhibitor deficiency". J. Clin. Pathol. 60 (5): 565–6. DOI:10.1136/jcp.2006.041350. PMID 17513516. Research Blogging.
  10. Anonymous. cyklokapron (tranexamic acid) injection, solution. U.S. National Library of Medicine. Retrieved on 2009-02-19.
  11. 11.0 11.1 Severino M, Bonadonna P, Passalacqua G (August 2009). "Large local reactions from stinging insects: from epidemiology to management". Curr Opin Allergy Clin Immunol 9 (4): 334–7. DOI:10.1097/ACI.0b013e32832d0668. PMID 19458526. Research Blogging.
  12. Mauriello PM, Barde SH, Georgitis JW, Reisman RE (October 1984). "Natural history of large local reactions from stinging insects". J. Allergy Clin. Immunol. 74 (4 Pt 1): 494–8. PMID 6491095[e]
  13. 13.0 13.1 Golden DB, Marsh DG, Freidhoff LR, et al. (December 1997). "Natural history of Hymenoptera venom sensitivity in adults". J. Allergy Clin. Immunol. 100 (6 Pt 1): 760–6. PMID 9438483[e]
  14. Schuberth KC, Lichtenstein LM, Kagey-Sobotka A, Szklo M, Kwiterovich KA, Valentine MD (April 1982). "An epidemiologic study of insect allergy in children. I. Characteristics of the disease". J. Pediatr. 100 (4): 546–51. PMID 7062201[e]
  15. Schuberth KC, Lichtenstein LM, Kagey-Sobotka A, Szklo M, Kwiterovich KA, Valentine MD (March 1983). "Epidemiologic study of insect allergy in children. II. Effect of accidental stings in allergic children". J. Pediatr. 102 (3): 361–5. PMID 6827407[e]
  16. Reisman RE (September 1992). "Natural history of insect sting allergy: relationship of severity of symptoms of initial sting anaphylaxis to re-sting reactions". J. Allergy Clin. Immunol. 90 (3 Pt 1): 335–9. PMID 1345753[e]
  17. Fernandez J, Soriano V, Mayorga L, Mayor M (February 2005). "Natural history of Hymenoptera venom allergy in Eastern Spain". Clin. Exp. Allergy 35 (2): 179–85. DOI:10.1111/j.1365-2222.2005.02169.x. PMID 15725189. Research Blogging.
  18. Golden DB, Kelly D, Hamilton RG, Craig TJ (June 2009). "Venom immunotherapy reduces large local reactions to insect stings". J. Allergy Clin. Immunol. 123 (6): 1371–5. DOI:10.1016/j.jaci.2009.03.017. PMID 19443022. Research Blogging.
  19. Salamone JA III and Pratt MA (2004), Dermatologic Emergencies: Immediate Recognition and Management of Life-Threatening Problems: Angioedema & Urticaria, in Stone CK and Humphries RL, Current Emergency Diagnosis & Treatment (Fifth Edition ed.), Lange/McGraw-Hill, at 1012-1013