I hope the test for amyloidosis
was a rectal biopsy with Congo Red stain that is still the gold standard.
The other option is angioedema
of tongue secondary to medications like lisinopril
etc (ACE-inhibitor group of drugs for controlling blood pressure).
It is not an allergy to the drug but rather a buildup of chemicals that cause swelling.
The 3rd possibility is consumption of C4 protein, that should be checked with serum Complement C4 levels (just a blood test
). If very low, you need additional scans like US or CT abdomen to exclude a secondary cause of low C4 levels.
I hope that was useful.