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This article is part of the series Hereditary angioedema - management consensus 2010.

Open Access Highly Accessed Review

Acquired angioedema

Marco Cicardi* and Andrea Zanichelli

Author Affiliations

Dipartimento di Scienze Cliniche "Luigi Sacco" Università di Milano, Milano Italy, Ospedale L.Sacco Milano, Italy

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Allergy, Asthma & Clinical Immunology 2010, 6:14  doi:10.1186/1710-1492-6-14

The electronic version of this article is the complete one and can be found online at: http://www.aacijournal.com/content/6/1/14


Received:26 April 2010
Accepted:28 July 2010
Published:28 July 2010

© 2010 Cicardi and Zanichelli; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Acquired angioedema (AAE) is characterized by acquired deficiency of C1 inhibitor (C1-INH), hyperactivation of the classical pathway of human complement and angioedema symptoms mediated by bradykinin released by inappropriate activation of the contact-kinin system. Angioedema recurs at unpredictable intervals, lasts from two to five days and presents with edema of the skin (face, limbs, genitals), severe abdominal pain with edema of the gastrointestinal mucosa, life-threateing edema of the upper respiratory tract and edema of the oral mucosa and of the tongue. AAE recurs in association with various conditions and particularly with different forms of lymphoproliferative disorders. Neutralizing autoantibodies to C1-INH are present in the majority of patients. The therapeutic approach to a patient with AAE should first be aimed to avoid fatalities due to angioedema and then to avoid the disability caused be angioedema recurrences. Acute attacks can be treated with plasma-derived C1-INH, but some patients become non-responsive and in these patients the kallikrein inhibitor ecallantide and the bradykinin receptor antagonist icatibant can be effective. Angioedema prophylaxis is performed using antifibrinolytic agents and attenuated androgens with antifibrinolytic agents providing somewhat better results. Treatment of the associated disease can resolve AAE in some patients.

Review

The symptoms

The three key elements of the syndrome commonly referred to as acquired angioedema (AAE), which was first described by Caldwell in 1972 [1], are acquired deficiency of C1 inhibitor (C1-INH), hyperactivation of the classical pathway of human complement and recurrent angioedema symptoms. It is considered a very rare condition with just more than 100 patients reported in the literature [2]. In absence of epidemiological data, we can only speculate about its prevalence. In our list of angioedema patients, we found 1 AAE every 10 patients with the hereditary form of C1-INH deficiency (hereditary angioedema, HAE). HAE minimal prevalence in the population is 1.41/100,000 and usual estimated prevalence between 1:10,000 and 1:50,000 [3,4]. Therefore, a very crude estimated prevalence of AAE could range between 1:100,000 and 1:500,000. We believe that the actual number is much higher than this because the condition is frequently unrecognized.

From the clinical point of view the angioedema symptoms that characterize AAE can not be differentiated from those present in HAE patients who have a deficiency of C1-INH due to mutations in one of the two alleles coding for this protein [5]. This could be anticipated based on the fact that in both forms angioedema is mediated by bradykinin episodically released by inappropriate activation of the contact-kinin system lacking its major physiologic regulator C1-INH [6,7]. Thus, similar to HAE patients, patients with AAE have no major urticaria flare. Angioedema recurs at unpredictable intervals, lasting from two to five days and presenting with disfiguring, non pitting, non-pruritic edema of the skin (face, limbs, genitals), severe abdominal pain for edema of the gastrointestinal mucosa leading to temporary bowel occlusion (Figure 1) [8], life-threateing edema of the upper respiratory tract and edema of the oral mucosa and of the tongue [2]. The only significant clinical difference between HAE and AAE is the age of onset of symptoms (Table 1): within the second decade of life for more than 90% of patients with HAE, after the fourth decade for those with AAE. Some additional minor differences can be found looking at different rates of recurrences at specific sites. Angioedema of the gastrointestinal mucosa causing abdominal pain is reported by nearly 80% of patients with HAE while less than 50% of our AAE patients and around 30% of those from Bouillet et al [9] reported such symptoms. Nevertheless, presentation of AAE with abdominal symptoms has been reported in our series and in the literature [10]. Cutaneous angioedema in HAE patients is typically localized to the extremities. Even if this location is also present in patients with AAE, in them angioedema recurs more frequently in the face than in the limbs [9] and we also noticed a rather frequent involvement of tongue and uvula; (Figure 2).

Table 1. Differences between acquired and hereditary angioedema due to C1-INH deficiency.

thumbnailFigure 1. Capsule endoscopy showing bowel occlusion due to angioedema of the gastrointestinal mucosa in a patient with C1-INH deficiency suffering from acute abdominal pain.

thumbnailFigure 2. Edema of the tongue in a patient with acquired angioedema.

The pathogenesis of the acquired defect of C1 inhibitor and the associated disease

In the first patients reported by Caldwell [1], AAE occurred in presence of lymphoma. This association has been repeatedly confirmed in subsequent patients [11-13] and even if lymphoma is not the only disease associated with AAE, it remains the preeminent disease association. Along with lymphoma, other benign forms of lymphoproliferation, namely monoclonal gammopathy of uncertain significance (MGUS), have been reported with high frequency in association with AAE. Capacity of lymphoma cells to deplete C1-INH or to cause its consumption through C1 activation, and the possibility to treat AAE by curing the underlying lymphoma, linked the lymphoproliferative disease to the pathogenesis of AAE [1,11-15]. In 1985, neutralizing autoantibodies to C1-INH were described in a few otherwise healthy patients [16,17]. Anti-C1-INH autoantibodies recognize epitopes around the reactive center of C1-INH and by binding these epitopes render the protein functionally inactive and/or increase its catabolism [18,19]. Autoantibody-mediated AAE seemed to be, at the beginning, a new type of AAE in which autoreactive immunoglobulins, instead of lymphoma tissues, was the cause of C1-INH depletion [20]. Re-evaluation of existing and new AAE patients demonstrated that autoantibodies could be present along with lymphoma and that the M component detected in several AAE patients corresponded to the anti-C1-INH autoantibodies [21]. Based on these findings, we can now see AAE as a condition with different form of abnormal B cell proliferation progressing from autoreactivity to malignant lymphoma. Whether the different degrees of lymphoproliferation found in AAE patients are evolutionary stages of the same process starting from expansion of anti-C1-INH autoreactive clone(s) has not yet been clarified [22].

Although lymphoproliferative diseases represent the main group encountered in AAE and a direct pathogenetic relationship between the two conditions can not be questioned, SLE, different neoplasias and infections have also been described in association with AAE [23-33]. The possibility chance association for some of these conditions can not be completely ruled out.

The diagnosis

AAE is first suspected in patients aged 40 or above who present with recurrent cutaneous and/or mucosal angioedema without urticaria, without an evident triggering factor, and without family history of angioedema. Measurement of C1-INH and C4 antigen in such patients is the first step. If both are normal, the deficiency of C1-INH is very unlike. If both are low (with C1-INH below 50% of normal on two separate determinations) diagnosis of C1-INH deficiency is made. If just C4 is reduced, C1-INH functional activity needs to be determined and if low (below 50% of normal on two separate determinations) diagnosis of C1-INH deficiency is made. Once this diagnosis has been made, additional testing is necessary to distinguish between inherited and acquired deficiency. This testing includes determination of C1q which is reduced in 70% of patients with AAE and is normal in HAE. If C1q is reduced, diagnosis of AAE can be established. If C1q is normal, autoantibodies to C1-INH can be investigated and their presence at high titre allows diagnosing AAE. If antibodies are negative, the diagnosis of AAE is assumed when complete screening of C1-INH gene gives no evidence of mutations affecting C1-INH protein. Major limits to this procedure are the inadequate availability and standardization of C1-INH functional measurements [34] and the possibility to look for anti-C1-INH autoantibodies only in a few specialized research laboratories. Therefore, careful harmonization of clinical and laboratory findings is mandatory to establish the diagnosis of AAE.

Patients with this diagnosis should undergo basic testing for lymphoproliferative and autoimmune disease. In addition to complete physical exam, we suggest that all patients have laboratory testing for complete blood cell count with differential, serum protein electrophoresis, antinuclear antibodies, chest X ray and abdominal ultrasound assessing lymphoid tissue. Due to the limited recurrences of other associated diseases, we do not see the need to systematically screen for other neoplasia or infection without specific clinical indications.

The treatment

The therapeutic approach to a patient with AAE should first be aimed to avoid fatalities due to angioedema and then to avoid the disability caused be angioedema recurrences. Angioedema- related fatalities derive from laryngeal edema. Based on the efficacy of replacement therapy with plasma-derived C1-INH in reverting laryngeal edema in patients with HAE [35], the same approach has been used for AAE. This treatment works in the majority but not in all AAE patients and in our experience some patient with AAE become progressively non responsive to plasma-derived C1-INH or need increased doses [5]. No other treatment for angioedema attacks has been extensively used in patients with AAE and therefore there is no established therapeutic alternative to plasma- derived C1-INH for life-threatening attacks. Non-responsive patients have just been assisted with invasive procedures aimed to maintain patency of upper airways during emergency. In recent years in a few AAE patients we have used two of the new treatments that have been proposed for HAE acute attacks: the kallikrein inhibitor ecallantide and the bradykinin B2 antagonist icatibant [36]. Since refractoriness to plasma-derived C1-INH is due to its autoantibody-mediated rapid catabolism, the use of drugs different from C1-INH but active in reversing HAE attacks have very good rationale for being effective in AAE. In fact from our limited experience response is extremely favourable. We treated 2 facial attacks in two patients with ecallantide and 1 laryngeal and 3 facial attacks in another patient with icatibant. Two of these patients were completely, and one partially, non-responsive to plasma derived C1-INH. All treated attacks responded very rapidly either to ecallantide or icatibant. The critical condition of C1-INH non-responder patients and the absence of licensed drugs strongly indicate the need for off-label treatments. Therefore, we recommend all our AAE patients always have 3000 U of plasma-derived C1-INH immediately available and treat attacks with 1500 U and repeating if ineffective. In the event of laryngeal edema, resuscitation facilities should be available. For those patients who have slow or no response, ecallantide or icatibant should be provided.

Reducing disability related to angioedema recurrences can be obtained by shortening attacks with an on-demand treatment with plasma-derived C1-INH, by preventing attacks with long term prevention with antifibrinolytics or androgens, or by curing the associated disease. The latter is the first choice when the associated disease has per se an indication to be treated. Resolution of the associated disease results in variable degrees of resolution of AAE from symptomatic improvement to complete biochemical and clinical recovery [13-15]. Treatment of the associated disease aimed only to control angioedema symptoms requires careful risk/benefit evaluation. Since most of the time the associated disease is lymphoproliferative, the choice to start a patient on chemotherapy or immunosuppressant is not always straightforward. Long-term treatment to prevent angioedema symptoms is often used in HAE and has also been used in AAE. While in HAE androgen derivatives are very effective prophylactic agents, results may not be as good in AAE. The reason for this is not totally clear. We know that attenuated androgens can increase the plasma levels of C1-INH [37]. Even if effective androgen doses in HAE do not require a measurable increase of C1-INH in plasma, it is still possible that these drugs relay on C1-INH production and their efficacy is less when C1-INH catabolism is very rapid [38]. In contrast, antifibrinolytic agents, the other class of drugs used for symptom prophylaxis in HAE [39,40], seem to have better efficacy in AAE than in HAE. It is assumed that the effect of these drugs in C1-INH deficient patients works through their anti-plasmin activity. Plasmin is critical for angioedema symptoms in C1-INH deficiency although the role is not clearly defined [41]. In AAE patients, the instability of the systems controlled by C1-INH is higher than in HAE and active plasmin is also generated separate from angioedema symptoms reinforcing the rationale for efficacy of antifibrinolytics in this condition [42-45]. At present, we consider antifibrinolytic agents as the first choice drug for angioedema prophylaxis in AAE. Prevention of attacks with continuous infusions of plasma-derived C1-INH has been attempted with controversial results and in our opinion having very little rationale [46,47]. The half life of plasma- derived C1-INH in HAE indicates two infusions per week as the minimum to maintain protective prophylactic plasma levels [48]. Even if one assumes that AAE patients will not require a more intensive program because of the faster C1-INH catabolism and will not increase the risk of becoming resistant to plasma-derived C1-INH, this prophylactic infusion regimen seems justified only for those patients with two or more severe attacks per week, a condition that we did not find in any of our 42 AAE patients. We reserve plasma-derived C1-INH infusions for on-demand treatment of severe angioedema events and do not use this for prophylaxis.

Competing interests

MC has consultancy agreement with Dyax, Pharming and Shire, is in advisory board and invited speaker of Dyax, Shire. CSL Behring. AZ has been Invited speaker for CSL Behring and Shire

Authors' contributions

MC wrote the review and AZ gave critical revision and collected the personal data that are reported. Both authors have read and approved the final manuscript.

Acknowledgements

Supported by Telethon grant n. GGP08223 and a grant from Invernizzi Foundation

References

  1. Caldwell JR, Ruddy S, Schur PH, Austen KF: Acquired C1 inhibitor deficiency in lymphosarcoma.

    Clin Immunol Immunopathol 1972, 1:39-52. Publisher Full Text OpenURL

  2. Zingale LC, Castelli R, Zanichelli A, Cicardi M: Acquired deficiency of the inhibitor of the first complement component: presentation, diagnosis, course, and conventional management.

    Immunol Allergy Clin North Am 2006, 26:669-90. PubMed Abstract | Publisher Full Text OpenURL

  3. Bygum A: Hereditary angio-oedema in Denmark: a nationwide survey.

    Br J Dermatol 2009, 161:1153-8. PubMed Abstract | Publisher Full Text OpenURL

  4. Zuraw BL: Clinical practice. Hereditary angioedema.

    N Engl J Med 2008, 359:1027-36. PubMed Abstract | Publisher Full Text OpenURL

  5. Agostoni A, Aygören-Pürsün E, Binkley KE, Blanch A, Bork K, Bouillet L, Bucher C, Castaldo AJ, Cicardi M, Davis AE, De Carolis C, Drouet C, Duponchel C, Farkas H, Fáy K, Fekete B, Fischer B, Fontana L, Füst G, Giacomelli R, Gröner A, Hack CE, Harmat G, Jakenfelds J, Juers M, Kalmár L, Kaposi PN, Karádi I, Kitzinger A, Kollár T, et al.: Hereditary and acquired angioedema: problems and progress: proceedings of the third C1 esterase inhibitor deficiency workshop and beyond.

    J Allergy Clin Immunol 2004, 114:S51-131. PubMed Abstract | Publisher Full Text OpenURL

  6. Nussberger J, Cugno M, Amstutz C, Cicardi M, Pellacani A, Agostoni A: Plasma bradykinin in angio-oedema.

    Lancet 1998, 351:1693-7. PubMed Abstract | Publisher Full Text OpenURL

  7. Davis AE: C1 inhibitor and hereditary angioneurotic edema.

    Annu Rev Immunol 1988, 6:595-628. PubMed Abstract | Publisher Full Text OpenURL

  8. Zingale LC, Zanichelli A, Deliliers DL, Rondonotti E, De Franchis R, Cicardi M: Successful resolution of bowel obstruction in a patient with hereditary angioedema.

    Eur J Gastroenterol Hepatol 2008, 20:583-7. PubMed Abstract | Publisher Full Text OpenURL

  9. Bouillet-Claveyrolas L, Ponard D, Drouet C, Massot C: Clinical and biological distinctions between type I and type II acquired angioedema.

    Am J Med 2003, 115:420-1. PubMed Abstract | Publisher Full Text OpenURL

  10. Eck SL, Morse JH, Janssen DA, Emerson SG, Markovitz DM: Angioedema presenting as chronic gastrointestinal symptoms.

    Am J Gastroenterol 1993, 88:436-9. PubMed Abstract OpenURL

  11. Schreiber AD, Zweiman B, Atkins P, Goldwein F, Pietra G, Atkinson B, Abdou NI: Acquired angioedema with lymphoproliferative disorder: association of C1 inhibitor deficiency with cellular abnormality.

    Blood 1976, 48:567-80. PubMed Abstract | Publisher Full Text OpenURL

  12. Hauptmann G, Lang JM, North ML, Oberling F, Mayer G, Lachmann P: Acquired c1-inhibitor deficiencies in lymphoproliferative diseases with serum immunoglobulin abnormalities. A study of three cases.

    Blut 1976, 32:195-206. PubMed Abstract | Publisher Full Text OpenURL

  13. Castelli R, Deliliers DL, Zingale LC, Pogliani EM, Cicardi M: Lymphoproliferative disease and acquired C1 inhibitor deficiency.

    Haematologica 2007, 92:716-8. PubMed Abstract | Publisher Full Text OpenURL

  14. Hauptmann G, Petitjean F, Lang JM, Oberling F: Acquired C1 inhibitor deficiency in a case of lymphosarcoma of the spleen. Reversal of complement abnormalities after splenectomy.

    Clin Exp Immunol 1979, 37:523-31. PubMed Abstract | PubMed Central Full Text OpenURL

  15. Levi M, Hack CE, van Oers MH: Rituximab-induced elimination of acquired angioedema due to C1-inhibitor deficiency.

    Am J Med 2006, 119:e3-5. PubMed Abstract | Publisher Full Text OpenURL

  16. Jackson J, Sim RB, Whelan A, Feighery C: An IgG autoantibody which inactivates C1-inhibitor.

    Nature 1986, 323:722-4. PubMed Abstract | Publisher Full Text OpenURL

  17. Alsenz J, Bork K, Loos M: Autoantibody-mediated acquired deficiency of C1 inhibitor.

    N Engl J Med 1987, 316:1360-6. PubMed Abstract | Publisher Full Text OpenURL

  18. Malbran A, Hammer CH, Frank MM, Fries LF: Acquired angioedema: observations on the mechanism of action of autoantibodies directed against C1 esterase inhibitor.

    J Allergy Clin Immunol 1988, 81:1199-204. PubMed Abstract | Publisher Full Text OpenURL

  19. Mandle R, Baron C, Roux E, Sundel R, Gelfand J, Aulak K, Davis AE, Rosen FS, Bing DH: Acquired C1 inhibitor deficiency as a result of an autoantibody to the reactive center region of C1 inhibitor.

    J Immunol 1994, 152:4680-5. PubMed Abstract | Publisher Full Text OpenURL

  20. Alsenz J, Loos M: The acquired C1-INH deficiencies with autoantibodies (AAE type II).

    Behring Inst Mitt 1989, (84):165-72. PubMed Abstract OpenURL

  21. Cicardi M, Beretta A, Colombo M, Gioffre D, Cugno M, Agostoni A: Relevance of lymphoproliferative disorders and of anti-C1 inhibitor autoantibodies in acquired angio-oedema.

    Clin Exp Immunol 1996, 106:475-80. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  22. Cugno M, Castelli R, Cicardi M: Angioedema due to acquired C1-inhibitor deficiency: a bridging condition between autoimmunity and lymphoproliferation.

    Autoimmun Rev 2008, 8:156-9. PubMed Abstract | Publisher Full Text OpenURL

  23. Nettis E, Colanardi MC, Loria MP, Vacca A: Acquired C1-inhibitor deficiency in a patient with systemic lupus erythematosus: a case report and review of the literature.

    Eur J Clin Invest 2005, 35:781-4. PubMed Abstract | Publisher Full Text OpenURL

  24. Nagy L, Hannema A, Swaak A: Acquired C1 inhibitor deficiency associated with systemic lupus erythematosus, secondary antiphospholipid syndrome and IgM monoclonal paraproteinaemia.

    Clin Rheumatol 1999, 18:56-8. PubMed Abstract | Publisher Full Text OpenURL

  25. Ochonisky S, Intrator L, Wechsler J, Revuz J, Bagot M: Acquired C1 inhibitor deficiency revealing systemic lupus erythematosus.

    Dermatology 1993, 186:261-3. PubMed Abstract | Publisher Full Text OpenURL

  26. Nakamura S, Yoshinari M, Saku Y, Hirakawa K, Miishima C, Murai K, Tokiyama K, Fujishima M: Acquired C1 inhibitor deficiency associated with systemic lupus erythematosus affecting the central nervous system.

    Ann Rheum Dis 1991, 50:713-6. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  27. Wasserfallen JB, Spaeth P, Guillou L, Pecoud AR: Acquired deficiency in C1-inhibitor associated with signet ring cell gastric adenocarcinoma: a probable connection of antitumor-associated antibodies, hemolytic anemia, and complement turnover.

    J Allergy Clin Immunol 1995, 95:124-31. PubMed Abstract | Publisher Full Text OpenURL

  28. Cohen SH, Koethe SM, Kozin F, Rodey G, Arkins JA, Fink JN: Acquired angioedema associated with rectal carcinoma and its response to danazol therapy. Acquired angioedema treated with danazol.

    J Allergy Clin Immunol 1978, 62:217-21. PubMed Abstract | Publisher Full Text OpenURL

  29. Varvarovska J, Sykora J, Stozicky F, Chytra I: Acquired angioedema and Helicobacter pylori infection in a child.

    Eur J Pediatr 2003, 162:707-9. PubMed Abstract | Publisher Full Text OpenURL

  30. Reche M, Caballero T, López-Trascasa M, Arribas JR, López Serrano MC: Angioedema and transient acquired C1 inhibitor functional deficiency in HIV infection: case report.

    Aids 2002, 16:1561. PubMed Abstract | Publisher Full Text OpenURL

  31. Farkas H, Gyeney L, Majthenyi P, Fust G, Varga L: Angioedema due to acquired C1-esterase inhibitor deficiency in a patient with Helicobacter pylori infection.

    Z Gastroenterol 1999, 37:513-8. PubMed Abstract OpenURL

  32. Minh D, Czink E, Fust G, Hollan SR: Acquired C1-esterase inhibitor deficiency and recurrent herpes infection in a patient with chronic lymphocytic leukemia.

    Diagn Immunol 1983, 1:68-71. PubMed Abstract OpenURL

  33. Cicardi M, Frangi D, Bergamaschini L, Gardinali M, Sacchi G, Agostoni A: Acquired C1 inhibitor deficiency with angioedema symptoms in a patient infected with Echinococcus granulosus.

    Complement 1985, 2:133-9. PubMed Abstract OpenURL

  34. Wagenaar-Bos IG, Drouet C, Aygören-Pursun E, Bork K, Bucher C, Bygum A, Farkas H, Fust G, Gregorek H, Hack CE, Hickey A, Joller-Jemelka HI, Kapusta M, Kreuz W, Longhurst H, Lopez-Trascasa M, Madalinski K, Naskalski J, Nieuwenhuys E, Ponard D, Truedsson L, Varga L, Nielsen EW, Wagner E, Zingale L, Cicardi M, van Ham SM: Functional C1-inhibitor diagnostics in hereditary angioedema: assay evaluation and recommendations.

    J Immunol Methods 2008, 338:14-20. PubMed Abstract | Publisher Full Text OpenURL

  35. Bork K, Barnstedt SE: Treatment of 193 episodes of laryngeal edema with C1 inhibitor concentrate in patients with hereditary angioedema.

    Arch Intern Med 2001, 161:714-8. PubMed Abstract | Publisher Full Text OpenURL

  36. Frank MM, Jiang H: New therapies for hereditary angioedema: disease outlook changes dramatically.

    J Allergy Clin Immunol 2008, 121:272-80. PubMed Abstract | Publisher Full Text OpenURL

  37. Gelfand JA, Sherins RJ, Alling DW, Frank MM: Treatment of hereditary angioedema with danazol. Reversal of clinical and biochemical abnormalities.

    N Engl J Med 1976, 295:1444-8. PubMed Abstract | Publisher Full Text OpenURL

  38. Melamed J, Alper CA, Cicardi M, Rosen FS: The metabolism of C1 inhibitor and C1q in patients with acquired C1- inhibitor deficiency.

    J Allergy Clin Immunol 1986, 77:322-6. PubMed Abstract | Publisher Full Text OpenURL

  39. Frank MM, Sergent JS, Kane MA, Alling DW: Epsilon aminocaproic acid therapy of hereditary angioneurotic edema. A double-blind study.

    N Engl J Med 1972, 286:808-12. PubMed Abstract | Publisher Full Text OpenURL

  40. Sheffer AL, Austen KF, Rosen FS: Tranexamic acid therapy in hereditary angioneurotic edema.

    N Engl J Med 1972, 287:452-4. PubMed Abstract | Publisher Full Text OpenURL

  41. Donaldson VH, Rosen FS, Bing DH: Role of the second component of complement (C2) and plasmin in kinin release in hereditary angioneurotic edema (H.A.N.E.) plasma.

    Trans Assoc Am Physicians 1977, 90:174-83. PubMed Abstract OpenURL

  42. Cugno M, Hack CE, de Boer JP, Eerenberg AJ, Agostoni A, Cicardi M: Generation of plasmin during acute attacks of hereditary angioedema.

    J Lab Clin Med 1993, 121:38-43. PubMed Abstract OpenURL

  43. Cugno M, Cicardi M, Agostoni A: Activation of the contact system and fibrinolysis in autoimmune acquired angioedema: a rationale for prophylactic use of tranexamic acid.

    J Allergy Clin Immunol 1994, 93:870-6. PubMed Abstract | Publisher Full Text OpenURL

  44. Cugno M, Cicardi M, Coppola R, Agostoni A: Activation of factor XII and cleavage of high molecular weight kininogen during acute attacks in hereditary and acquired C1-inhibitor deficiencies.

    Immunopharmacology 1996, 33:361-4. PubMed Abstract | Publisher Full Text OpenURL

  45. Cugno M, Cicardi M, Bottasso B, Coppola R, Paonessa R, Mannucci PM, Agostoni A: Activation of the coagulation cascade in C1-inhibitor deficiencies.

    Blood 1997, 89:3213-8. PubMed Abstract | Publisher Full Text OpenURL

  46. Levi M, Choi G, Picavet C, Hack C: Self-administration of C1-inhibitor concentrate in patients with hereditary or acquired angioedema caused by C1-inhibitor deficiency.

    J Allergy Clin Immunol 2006, 117:904-8. PubMed Abstract | Publisher Full Text OpenURL

  47. Bork K, Witzke G: Long-term prophylaxis with C1-inhibitor (C1 INH) concentrate in patients with recurrent angioedema caused by hereditary and acquired C1-inhibitor deficiency.

    J Allergy Clin Immunol 1989, 83:677-82. PubMed Abstract | Publisher Full Text OpenURL

  48. Martinez-Saguer I, Rusicke E, Aygören-Pürsün E, von Hentig N, Klingebiel T, Kreuz W: Pharmacokinetic analysis of human plasma-derived pasteurized C1-inhibitor concentrate in adults and children with hereditary angioedema: a prospective study.

    Transfusion 2010, 50:354-60. PubMed Abstract | Publisher Full Text OpenURL