S6152 Recurrent Paroxysmal Abdominal Pain From Acquired Angioedema Due to C1-Inhibitor Deficiency (AAE-C1-INH) in a Patient With B-Cell Chronic Lymphocytic Leukemia

Introduction: Angioedema is swelling involving subcutis and submucosa often associated with acute presentations of urticaria, and upper airway swelling. It can either be hereditary or acquired with the latter commonly linked to bradykinin-mediated associated with ACE-i use, or drug-induced (nonsteroidal anti-inflammatory drugs, statins). We present a rare case of isolated chronic gastrointestinal angioedema secondary to B-cell chronic lymphocytic leukemia i.e. Acquired Angioedema Due to C1-Inhibitor Deficiency (AAE-C1-INH) treated with tranexamic acid. Case Description/Methods: A 76-year-old man with a history of CLL stage 3, atrial fibrillation on DOAC, coronary artery disease, HFrEF, and gastroesophageal reflux disease presented with a 2-year history of recurrent, paroxysmal, intractable abdominal pain, often necessitating hospitalization. Episodes were accompanied by bloating, rigidity, nausea, vomiting, and alternating constipation and explosive diarrhea. These self-resolved with supportive care and bowel management. Multiple computed tomography abdomen scans were often inconclusive, though some revealed mild to moderate small bowel thickening. Esophagogastroduodenoscopy and colonoscopy with biopsies were negative for microscopic/lymphocytic/collagenous colitis and malignancy, as were infectious workups. Given the small bowel findings and extensive negative workup, a double balloon enteroscopy was performed, revealing a normal colon and 200 cm of ileum from the ICV. The patient consistently denied urticaria or airway swelling, and his medication list showed no high-risk angioedema drugs. However, due to the rare association between acquired angioedema and B-cell CLL, complement levels were drawn, showing low C4, functional C1 esterase inhibitor, C1q, and normal C3. Acquired angioedema was diagnosed, and the patient was referred to Immunology, who initiated treatment with tranexamic acid (TXA). Subsequently, the frequency and severity of his abdominal episodes significantly decreased. Discussion: This case highlights a rare cause of chronic paroxysmal abdominal pain: acquired angioedema due to C1-inhibitor deficiency (AAE-C1-INH) secondary to B-cell CLL. In CLL patients with unexplained GI symptoms even without dermatological and upper airway angioedema signs, and inconclusive imaging, endoscopy, malignancy and infectious workups, consider screening for AAE. Tranexamic acid can be an effective therapy, inhibiting the conversion of plasminogen to plasmin, thereby reducing the activation of the kallikrein-kinin system and subsequent bradykinin production.