Severe Familial Chylomicronemia Syndrome With Refractory Hypertriglyceridemia and Multisystem Complications Managed With Chronic Plasmapheresis and Olezarsen: A Case Report.

Familial chylomicronemia syndrome (FCS) is a rare, inherited lipid disorder characterized by severe hypertriglyceridemia and a risk of recurrent pancreatitis. Patients with biallelic pathogenic variants affecting lipoprotein lipase (LPL)-mediated triglyceride metabolism may remain refractory to conventional lipid-lowering therapies and strict dietary control, leading to recurrent critical illness and progressive multisystem complications. We report a female patient with genetically confirmed FCS and persistent triglyceride levels typically in the 4,000-5,000 mg/dL range despite adherence to diet and lipid-lowering therapy, without clear secondary contributors to severe hypertriglyceridemia. Her course included recurrent intensive care unit (ICU) admissions for hypertriglyceridemia-associated pancreatitis requiring insulin drips, with progression to chronic pancreatitis, pancreatic insufficiency requiring enzyme replacement, insulin-dependent diabetes with continuous glucose monitoring (CGM), chronic pain syndrome with opioid dependence concerns, and psychiatric comorbidity. During a hospitalization approximately 10 months prior to the most recent follow-up, the patient underwent placement of a right chest tunneled central venous catheter and initiated therapeutic plasmapheresis. She was concurrently followed by a triglyceride clinic and continued on olezarsen. At follow-up on February 25, 2025, she reported no hospitalizations since April 2024. A triglyceride value of 4,700 mg/dL was documented shortly before a scheduled plasmapheresis session. This case highlights the complexity of severe FCS when hypertriglyceridemia remains refractory to conventional management and illustrates a care pathway in which chronic outpatient plasmapheresis combined with emerging RNA-based therapy was associated with stabilization and avoidance of recurrent hospitalization. Sustained outpatient success required multidisciplinary coordination, addressing pancreatitis sequelae, glycemic management, chronic pain, psychiatric disease, and central-line monitoring. These observations are hypothesis-generating and highlight the potential role of coordinated outpatient plasmapheresis and emerging RNA-based therapies in the management of severe FCS. To our knowledge, reports describing long-term outpatient stabilization of severe FCS using combined chronic plasmapheresis and apolipoprotein C-III (APOC3)-targeted RNA therapy remain limited, and this case highlights a potential care pathway for patients with refractory disease.