A 34-year-old woman presents with recurrent episodes of faci…
A 34-year-old woman presents with recurrent episodes of facial swelling, abdominal pain, and nausea over the past two years. She denies urticaria during these episodes. Her mother had similar symptoms. She takes no angiotensin-converting enzyme inhibitors or nonsteroidal anti-inflammatory drugs. Laboratory testing reveals a low complement C4 level.Which of the following is the most appropriate next diagnostic step and preferred treatment for an acute laryngeal attack?