Narrative: 70 yo M with PMH of HTN, NIDDM, CKD3b, hypothyroidism, & multiple food allergies as documented below; presenting for evaluation of lower lip swelling. Patient states that he received the 2ndst Moderna COVID vaccine on Saturday (3/13) & felt fatigued that night but back to his normal baseline on Sunday. Monday morning (3/15), patient awoke to get ready to head out of town to an auction. At some point while getting ready, he noticed that he was having mild substernal chest pain described as sharp, constant, and nonradiating with no associated shortness of breath, dizziness, or diaphoresis. The pain was not worsened by exertion & persisted for approximately 4-5 hours before spontaneously resolving. He states that this pain did not feel like the pain he experienced with his previous 2 heart attacks in 2018 & 1999; almost more like something was stuck in his chest. Later that morning, patient became acutely diaphoretic. He felt this was likely secondary to hypoglycemia but did not have his meter on him to check his sugar. He ate some chocolate with resolution of symptoms. Patient felt well the remainder of the afternoon until when he got back home around 8:30pm. At that time, he noted new onset of itching around his anterior waist with associated hives located along the anterior band of his pants. Less than 1 hour later, he noted rapid-onset of lower lip swelling, 2-3x normal, with drooling. He denies associated nausea, vomiting, wheezing, chest tightness, abdominal pain, difficulty swallowing. Patient denies ever experiencing similar episodes of swelling & denies any interval known exposure to onions, papayas, pistachios, or mangos. He is unaware of any family history of idiopathic swelling, though notes he is not in communication with any family members & is unable to accurately attest to any medical problems. Patient does currently take lisinopril and has been on this for several years. HOSPITAL COURSE: Patient presented for evaluation of facial angioedema with associated pruritic urticaria which began atypical chest pain occurring earlier that morning. At time of presentation, patient was hemodynamically stable with obvious lower lip & lower facial swelling. He had no appreciable wheezing or tongue, uvular, or laryngeal edema. He did exhibit some slurred speech secondary to the lip swelling. No major lab abnormalities. Marked improvement with Solumedrol 125mg, famotidine 20mg IV, Benadryl 50mg, NS 500cc bolus; patient initiated on HI-heparin gtt in the ED. Patient additionally assessed by CM who agreed with management. Patient transferred to SDU for monitoring, with almost complete resolution of swelling overnight, patient deemed stable for discharge the following morning. Given timecourse of onset of angioedema over minutes to hours with associated urticaria and no obvious exposure to known triggers, feel this is most likely histamine-mediated idiopathic angioedema. CBC, BMP, LFTs, ESR/CRP unremarkable, C4 not obtained. Patient observed overnight without worsening of reaction. Discontinued lisinopril - although suspicion that this is ACE-induced is low, would still recommend avoidance & change to ARB. Patient had several hours of atypical chest pain prior to admission that had completely resolved at time of admission. Troponin undetectable with reassuring EKG showing NSR with no ST changes. Patient started on HI-heparin gtt in ED with concern for PE given recent chest pain with elevated D-dimer (Wells score 0). CTA deferred in setting of CKD3b. Patient remained asymptomatic and not hypoxic, satting 95% on RA with no evidence of R heart strain on POC US. Re- evaluation determined suspicion for PE extremely low and heparin gtt was discontinued. Home coreg maintained for HTN. Discontinued home lisinopril as above.