S6462 Gastric Transthyretin Amyloidosis: A Unique Case of Gastric Outlet Obstruction and Gastroparesis

Introduction: Gastric transthyretin amyloidosis (ATTR) affects the interstitial cells of Cajal, which are pivotal for gastric motility. The rare complications include gastroparesis secondary to autonomic neuropathy and gastric outlet obstruction (GOO) due to pyloric stenosis from fibril deposits. The exact incidence and prevalence of the disease with these complications are currently unknown. We present a unique case of hereditary ATTR complicated with recurrent GOO and gastroparesis requiring a gastric simulator. Case Description/Methods: An 80-year-old woman with a past medical history of hereditary transthyretin cardiac amyloidosis presented with persistent nausea and vomiting. The admission vital signs were stable, with a benign physical examination, and labs were pertinent for hypokalemia and hyperchloremic metabolic alkalosis. She received antiemetics without any relief. Subsequently, the computed tomography (CT) abdomen revealed thickened gastric folds. This prompted an esophagogastroduodenoscopy (EGD), which revealed retained food in the stomach, raising concerns for gastroparesis. The pyloric junction was stenosed and required balloon catheter dilation. The EGD biopsy showed amyloid deposits in the gastric wall, positive for Congo red stain. Immunohistochemistry detected ATTR. After the EGD, her symptoms initially improved, and on discharge, she continued Tafamidis and Eplontersen. Three months later, she was hospitalized again with persistent vomiting, not responding to any antiemetics. She required a repeat EGD with pyloric dilation. Following a multidisciplinary team approach, a joint decision was made to place a gastric simulator for refractory vomiting. After this intervention, her symptoms improved significantly, and she closely followed up with the gastroenterologist. Discussion: Gastrointestinal symptoms in ATTR are often nonspecific, making diagnosis challenging; therefore, a high clinical suspicion is warranted to establish a definitive diagnosis promptly. The mainstay treatments for gastric ATTR are disease-modifying therapies (TTR stabilizers and gene silencing). Moreover, a gastric simulator is used as a last resort for patients with gastric ATTR complicated with gastroparesis who haven't responded to other treatments. Due to the rare co-occurring complications and underreported incidence, we aim to raise awareness and strongly advocate for the need for large, multi-center, prospective studies to capture the impact of gastric ATTR and its burden on the US healthcare system.