Thank you for your inquiry.
First of all, I think you have done due diligence in your search for a cause, and I do not feel any further laboratory evaluation is indicated. Based on the history and lab data obtained so far, this patient appears to have idiopathic angioedema. Unfortunately, as you well know, this accounts for the vast majority of cases of angioedema, and in such instances, the cause simply alludes us. In addition, also unfortunately, therapy for idiopathic angioedema leaves much to be desired since patients usually do not respond to antihistamine treatment. In fact, oftentimes they are resistant to all preventive therapy and quite often respond only to epinephrine injection for acute episodes.
More recently this form of angioedema has been called nonhistaminergic angioedema, and has been hypothesized to be due to activation of the contact system and therefore mediated by kinins. In fact, treatment with a bradykinin-2 receptor antagonist, icatibant, a drug we normally use for hereditary angioedema, has been found to be successful in this disorder (1).
Thus, one way to approach this patient if the symptoms are severe is to try icatibant if you can get it authorized for administration.
Except for this, there is no other approach that has been consistently successful in the management of cases such as the one you described.
Thank you again for your inquiry and we hope this response is helpful to you.
1. Annals of Allergy, Asthma, and Immunology 2012; 108(6):460-461.
Phil Lieberman, M.D.