What Is Familial Chylomicronemia Syndrome?
Published on October 29, 2025
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Familial chylomicronemia syndrome (FCS) is a rare genetic disorder that makes it difficult for the body to break down fat particles in the blood. These excess fats (triglycerides) and particles that carry them (chylomicrons) most commonly cause inflammation of the pancreas, but they can also affect your skin, eyes, and liver.
With FCS, triglyceride levels can be 10 times higher than normal, even without eating. No treatments can cure FCS, but following a very low-fat diet can improve symptoms.
Types of Familial Chylomicronemia Syndrome
Familial chylomicronemia syndrome doesn’t have true “types,” but experts can identify the condition by the factors that cause it, which can differ from person to person. These include inherited deficiencies of:
- GPIHBP1: A protein that helps break down and process fats
- Apolipoprotein A5: A gene that regulates blood triglyceride levels
- Apolipoprotein C-II: A type of protein that breaks down fats
- Lipase maturation factor 1: A protein that plays a critical role in fat digestion
- Lipoprotein lipase: An enzyme that helps with processing of blood triglycerides
Signs and Symptoms of Familial Chylomicronemia Syndrome
Symptoms of familial chylomicronemia syndrome can start as early as infancy, but some people don’t have symptoms until adulthood. Extremely high triglyceride levels, which can be up to 10 times higher than normal, can provoke symptoms in several body systems.
Common FCS symptoms include:
- Abdominal pain from pancreatitis (pancreas inflammation)
- Enlargement of the liver and spleen (hepatosplenomegaly)
- Creamy appearance of blood vessels in the eye (lipemia retinalis)
- Yellow fatty deposits (xanthomas) in the skin of the back, buttocks, feet, ankles, knees, and elbows
Less common symptoms of FCS are:
- Emotional dysregulation
- Unexpected weight loss
- Memory loss
- Depression
- Colic in infants
- Joint pain
- Weakness and fatigue
- Nausea and vomiting
- Bloating and indigestion
- Abscesses around the anus
- Yellowing of the skin or eyes (jaundice)
- Insufficient growth in children (failure to thrive)
- Dangerous blood clots in the lung (pulmonary embolism)
Causes and Risk Factors of Familial Chylomicronemia Syndrome
Genetic mutations inherited from parents is the primary cause of familial chylomicronemia syndrome. When the DNA code of a particular gene is incorrect, the gene does not work properly, and the chain of events that is supposed to work together to break down fats gets interrupted.
Any break in that chain can keep your body from processing dietary fat, which allows chylomicrons (fat-carrying particles) to build up in your bloodstream (chylomicronemia). You may have a higher risk of developing FCS if you have a family history of combined hyperlipidemia (high cholesterol and triglycerides) or hypertriglyceridemia (high triglyceride levels in the blood) and also:
- Have type 2 diabetes
- Have obesity
- Consume large amounts of alcohol
- Have chronic kidney disease with pregnancy
Some medications may also increase your risk, including corticosteroids, immunosuppressive drugs, antipsychotics, antidepressants, and drugs that treat heart problems.
How Is Familial Chylomicronemia Syndrome Diagnosed?
To diagnose familial chylomicronemia syndrome, your healthcare provider will ask you about your health history and your family’s medical history, and do a physical examination to check for an enlarged liver and spleen or fatty deposits under your skin.
Common blood tests for FCS include:
- Fasting lipid panels
- Apolipoprotein B (APO B)
- Thyroid-stimulating hormone (TSH)
- Hemoglobin A1C (HbA1C) to rule out diabetes
- Serum transaminases to check liver function
- Creatinine to assess kidney function
Triglyceride levels will be extremely high: over 750 milligrams per deciliter (mg/dL) compared with the typical level of less than 150 mg/dL. When you have FCS, the lab technician will also see a creamy layer (the extra fat cells) in the tube after they draw your blood and spin it for analysis.
In addition to blood tests, your provider may want to check your urine for glucose, protein, and other markers.
You may also need these tests:
- CT scan to check for pancreatitis
- Ultrasound of the right upper abdomen to rule out gallstones
- Genetic tests to identify DNA mutations
- Eye exam to spot fatty deposits in the retina
Treatment and Medication Options for Familial Chylomicronemia Syndrome
Treatment for familial chylomicronemia syndrome involves several specialties, often including an endocrinologist or lipidologist, dietitian, and primary care physician. Each of these specialists may recommend treatment.
Diet Modification
The primary treatment for familial chylomicronemia syndrome is following a very low-fat diet. With FCS, fat intake should stay less than 10 to 15 percent of your daily calories. This averages to about 20 to 30 grams (0.7 to 1.1 ounces) of fat per day, which can be difficult to keep up.
Good FCS diet options include vegetables, whole grains, beans, lean proteins, and some fruit and fat-free milk products with no added sugar.
Medication Options
In 2024, the U.S. Food and Drug Administration approved olezarsen (Tryngolza), a medication injected monthly, to be used along with diet to treat FCS. Olezarsen binds to genetic material that allows better processing and removal of fats in the blood.
Other medications, like the investigational drug plozasiran, are being studied in clinical trials in the United States, and volanesorsen (Waylivra) has been approved in Europe.
Plasmapheresis
In some situations, you may need a therapy called plasmapheresis: a medical procedure that extracts your blood plasma, removes excess triglycerides and toxic substances, then returns the plasma to your body. Plasmapheresis can decrease triglyceride levels by up to 97 percent, but the results aren’t permanent.
This procedure can have side effects like too much calcium in the blood, allergic reactions, unstable blood pressure, infections, blood clots, and bleeding — and for many, the risks are too great and don’t outweigh the benefits. But your provider may recommend plasmapheresis if you have a severe episode of pancreatitis or if you are pregnant, because high triglyceride levels can affect fetal growth and may promote gestational diabetes.
Complementary Therapies
Because of strict dietary restrictions, some people with FCS have nutritional deficiencies. Your doctor may monitor vitamin and other nutrient levels and recommend supplements like fat-soluble vitamins (A, D, E, and K) and fatty acids like alpha-linolenic acid, which don’t increase triglyceride levels.
Prevention of Familial Chylomicronemia Syndrome
Because familial chylomicronemia syndrome is an inherited condition, you can’t prevent it. But you can prevent complications of the disorder by following your treatment plan and avoiding alcohol. Some medications can also increase triglyceride levels, so your provider may recommend some changes. Be sure not to stop any of your medications without first consulting your provider.
Lifestyle Changes for Familial Chylomicronemia Syndrome
Certain lifestyle changes can help you lessen your familial chylomicronemia syndrome symptoms. A very low-fat diet plays a huge role in the management of FCS. Most symptoms arise from extremely high blood triglyceride levels, so reducing fat in your diet can improve these symptoms significantly.
It’s also important to avoid drinking alcohol, which can increase the amount of fats in your bloodstream.
In addition to dietary changes, regular exercise and maintaining a healthy weight can decrease triglyceride levels and improve symptoms.
Familial Chylomicronemia Syndrome Condition Prognosis
While a low-fat diet can improve symptoms of familial chylomicronemia syndrome, you may still have periods of fatigue, stomach upset, and abdominal pain. FCS also increases the risk of heart conditions.
These symptoms can be tough to deal with, and some people with FCS also report mental health issues like depression. If you feel overwhelmed by your diagnosis, reach out to one of the organizations listed below for support from peers, access to the latest FCS news, and information about clinical trials.
Complications of Familial Chylomicronemia Syndrome
The most common complication of familial chylomicronemia syndrome is chronic pancreatitis, which can lead to cysts, problems secreting digestive enzymes, and sometimes breakdown of pancreas tissue. When severe enough, acute pancreatitis can cause failure of multiple organs — a dangerous situation requiring hospitalization.
Ongoing abdominal pain from pancreatitis often sparks anxiety, and some people with FCS report other mental health complications like depression, social anxiety, memory loss, and trouble concentrating. Very high triglycerides in your blood can also cause heart disease and increase your risk of cardiac events like heart attacks.
During pregnancy, FCS can slow fetal growth in the third trimester, and pregnant people may be more likely to develop pancreatitis with the condition. If you are pregnant, your provider may recommend monitoring triglyceride levels often to guide treatment decisions.
Research and Statistics: Who Has Familial Chylomicronemia Syndrome?
Familial chylomicronemia syndrome is a rare condition, and prior research shows that FCS affects only 1 to 10 people per every million. Because of its vague symptoms, though, some experts believe FCS may be underreported and underdiagnosed.
No studies have found that specific genders or racial groups experience FCS more than others, but there have been more cases diagnosed in French Canadians and Afrikaners.
Related Conditions
Familial chylomicronemia syndrome is related to some other conditions, which must be ruled out before a diagnosis of FCS can be made. These include:
- Gallstones, which block the bile duct (which drains the pancreas) and can cause pancreatitis
- Alcoholic pancreatitis, caused by heavy alcohol use
- Insulin resistance, which means insulin can’t manage blood sugar levels well
- Severe hypothyroidism, which happens when your thyroid doesn’t produce enough thyroid hormone
- Metabolic syndrome, caused by insulin resistance and which can lead to high triglyceride levels
Support for People With Familial Chylomicronemia Syndrome
This global support network promotes advocacy and provides education for people living with familial chylomicronemia syndrome and their families. They offer FCS-friendly recipes and dietary recommendations to make life easier with FCS.
National Organization for Rare Disorders (NORD)
NORD offers support for anyone with a rare disorder like FCS through patient assistance programs, FCS information, and access to specialized care for familial chylomicronemia syndrome. They can also help with financial hardships and have a free helpline for questions about FCS and available support or clinical trials.
The Takeaway
- Familial chylomicronemia syndrome is a rare inherited disorder that causes very high levels of fat cells (triglycerides and chylomicrons) in the bloodstream.
- FCS causes symptoms like severe abdominal pain from pancreatitis, fatty deposits under the skin, and an enlarged spleen and liver, but it can sometimes cause other symptoms like anxiety, weakness, and joint pain.
- The most commonly prescribed treatment for familial chylomicronemia syndrome is a very low-fat diet, but the FDA recently approved a medication that can lower triglyceride levels in the blood, and more medications are on the path to approval.
FAQ
What causes familial chylomicronemia syndrome?
Familial chylomicronemia syndrome is caused by a genetic mutation inherited from one or both parents.
How do you treat familial chylomicronemia syndrome?
The most common method for treating FCS is a very low-fat diet, but the FDA has also approved a new medication called olezarsen (Tryngolza), which can help lower the levels of fat in the bloodstream.
How rare is FCS?
FCS is very rare, and only 3,000 to 5,000 people across the world have the disorder.
How do you test for familial chylomicronemia syndrome?
Healthcare providers test for FCS by checking triglyceride levels in the blood, which can be up to 10 times higher than normal.
Resources We Trust
- Mayo Clinic Hypertriglyceridemic pancreatitis
- Cleveland Clinic Hypertriglyceridemia
- National Organization for Rare Disorders Familial Chylomicronemia Syndrome
- American Society of Gene & Cell Therapy FDA Approves RNA-targeted Therapy for Familial Chylomicronemia Syndrome
- Foundation of the National Lipid Association Low-Fat Cookbook for Patients with FCS
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
- Metkus TS et al. Chylomicronemia Syndrome. MedlinePlus. May 8, 2024.
- Regmi M et al. Familial Hyperchylomicronemia Syndrome. StatPearls. August 8, 2023.
- Familial Chylomicronemia Syndrome. National Organization for Rare Disorders. February 3, 2025.
- GPIHBP1 glycosylphosphatidylinositol anchored high density lipoprotein binding protein 1 [Homo sapiens (human)]. National Center for Biotechnology Information. August 19, 2025.
- APOA5 apolipoprotein A5 [Homo sapiens (human)]. National Center for Biotechnology Information. August 19, 2025.
- Wolska A et al. Apolipoprotein C2. Atherosclerosis. October 20, 2017.
- Dabravolski SA et al. The Role of Lipase Maturation Factor 1 in Hypertriglyceridaemia and Atherosclerosis: An Update. Sage Open Medicine. October 16, 2024.
- Pirahanchi Y et al. Biochemistry, Lipoprotein Lipase. StatPearls. July 30, 2023.
- Familial Chylomicronemia Syndrome. Genetic and Rare Diseases Information Center. September 2025.
- Goldberg RB et al. A Comprehensive Update on the Chylomicronemia Syndrome. Frontiers in Endocrinology. October 23, 2020.
- Javed F et al. Familial Chylomicronemia Syndrome: An Expert Clinical Review From the National Lipid Association. Journal of Clinical Lipidology. June 23, 2025.
- Triglycerides: Why Do They Matter? Mayo Clinic. September 3, 2022.
- FDA Approves Drug to Reduce Triglycerides in Adult Patients With Familial Chylomicronemia Syndrome. U.S. Food and Drug Administration. December 19, 2024.
- Tryngolza Prescribing Information. U.S. Food and Drug Administration. 2024.
- Bashir M et al. Hyperlipidaemia and Severe Hypertriglyceridaemia in Pregnancy. The Obstetrician & Gynaecologist. June 10, 2023.
- Dos Santos F et al. Familial Chylomicronaemia Syndrome in Pregnancy – Report of Two Cases Managed With Plasma Exchange. Obstetric Medicine. September 19, 2024.
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Anna C.E. Hurst, MD, MS, FACMG
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Anna C. E. Hurst, MD, is a medical geneticist with board certification in clinical genetics and pediatrics. She is an associate professor in the department of genetics at Universit...
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Abby McCoy is an experienced registered nurse who has worked with adults and pediatric patients encompassing trauma, orthopedics, home care, transplant, and case management. She is...