A 67 year-old man presents with lower lip swelling for the past two hours, and tells you he was recently diagnosed with acquired C1 esterase inhibitor deficiency. He has normal vitals, is speaking in full sentences, and denies any sensation of tongue or airway swelling. What do you do next? Easy, right? In addition to closely monitoring the patient for developing airway compromise, you need to replace their C1 esterase inhibitor! But how exactly does that work?
C1 esterase inhibitor can be replaced a number of ways (a refresher on the bradykinin/complement pathway can be found here):
- human plasma-derived C1INH concentrate (pdC1INH), brand name Berinert, administered as 20mg/kg IV
- recombinant C1INH (rC1INH), brand name Ruconest, administered as 50mg/kg IV
- FFP (which contains C1 esterase inhibitor and also contains ACE, which degrades bradykinin)
- bradykinin 2 -receptor inhibitor, brand name Icatibant, administered as a fixed 30mg subcutaneous injection
- kallikrein inhibitor, brand name Ecallantide, administered as three 10mg subcutaneous injections
After administration of one of the above, the patient should be observed until there is definite improvement, generally a few hours. Those with severe angioedema or frequent recurrent episodes of unclear etiology should be admitted. However, patients who have established C1 esterase inhibitor deficiency may know their disease and their symptoms better, and Berinert has been approved for self-administration, so certain patients may not need to be watched for as long.
At Sinai, we have Ruconest available, though this patient was actually given Berinert due to a pharmacy/quality issue with mixing the Ruconest. This patient noted significant improvement within several minutes of receiving the injection, and was discharged with close allergy follow up.
Special thanks to Dr. Moira Carroll for inspiring this pearl, and to patient JM, who generously consented for these photos to be taken and published.