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Case report
Acquired complement C1 esterase inhibitor deficiency in a patient with a rare SERPING1 variant with unknown significance
  1. Eva Rye Rasmussen1,2,
  2. Kasper Aanæs1,
  3. Marianne Antonius Jakobsen3 and
  4. Anette Bygum2,4
  1. 1 Otorhinolaryngology, Head and Neck Surgery and Audiology, Rigshospitalet, Kobenhavn, Denmark
  2. 2 OPEN, Clinical Institute, University of Southern Denmark, Odense, Denmark
  3. 3 Department of Clinical Immunology, Odense University Hospital, Odense, Denmark
  4. 4 Dermatology and Allergy, Odense University Hospital, Odense, Denmark
  1. Correspondence to Dr Anette Bygum, anette.bygum{at}


Angioedema (AE) is caused by a wide range of diseases and pharmaceuticals; it can become life-threatening when located to the airways. Patients with deficiency or malfunction of complement C1 esterase inhibitor (hereditary or acquired) experience recurrent AE due to an accumulation of the vasoactive mediator bradykinin (BK). Complement C1 inhibitor normally decreases BK production, so a reduced function hereof causes increased levels. The diagnosis of hereditary or acquired AE can be difficult due to similarities to allergic reactions (swelling, abdominal pain, rash). We describe a 35-year-old man presenting with upper-airway AE progressing rapidly and promptly required cricothyroidotomy. Complement and autoantibody screening together with sequencing of SERPING1 were performed and gave the diagnosis of acquired complement C1 esterase inhibitor deficiency. The patient is unusual to have this disease before the age of 40 years. No associated comorbidities were found. It is important to know that antiallergic medication is not effective in BK-mediated AE.

  • genetics
  • immunology
  • dermatology

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  • Contributors ERR: consulted about the patient, wrote the manuscript, found references and approved the final edition. KA: treated the patient, critically revised the manuscript and approved the final edition. MAJ: critically revised the manuscript and approved the final edition. AB: treated the patient, came up with the clinical assessment, critically revised the manuscript and approved the final edition.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests AB has been involved in clinical trials and research with the following companies: Biocryst, Shire/Takeda, Dyax and CSL Behring. ERR has recieved research gants from CSL Behring and Shire/Takeda.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Patient consent for publication Obtained.