This patient was on ACE Inhibitor.
As you can see only the tongue is grossly affected. The sparing of immediate structures can be typical of angioedema. On the contrary, urticaria/anaphylactic edema can be more diffuse with the lips involved or the entire face swollen. In this patient, the lack of itching, erythema and other histaminic symptoms helped to steer away from hives (allergic reactions).
Investigations: Complement C4 concentration which is a good screening test for Hereditary angioedema (HAE) was normal. C1inh concentrations can also be measured to exclude HAE. So it was assumed that this is due to ACEi which he was on.
Prognosis: After nasal intubation he recovered in less than 24 hrs and was extubated the next day.
Image courtesy: NEJM