Familial Chylomicronemia Syndrome (FCS)


Familial chylomicronemia syndrome (FCS) is a rare genetic disorder estimated to affect 1-2 individuals per million. It is a serious disease that prevents the body from breaking down fats consumed through the diet, or triglycerides. These triglycerides are carried in the blood by large structures called chylomicrons.  Chylomicrons help move triglycerides to different parts of the body where they are needed for energy and fat storage.

While several genetic causes have been associated with FCS, about 80% of people with FCS have a problem with lipoprotein lipase. Lipoprotein lipase is a digestive enzyme in the blood that helps the body break down chylomicrons. People who have FCS are either unable to make lipoprotein lipase, or have a broken form of it. When lipoprotein lipase is absent or not working properly, chylomicrons build up in the blood, and triglyceride levels rise.

Normal triglyceride levels in the blood are less than 150 mg/dL. With FCS, it is not uncommon for triglyceride levels to exceed 1,000 mg/dL, even after medications and/or a low-fat diet are introduced.

Symptoms of FCS

Because FCS is an inherited disorder, symptoms and signs can develop as early as infancy or childhood, and commonly by adolescence.  Some patients will not present with symptoms until adulthood. Common signs include:

  • Lipemia Retinalis - a condition in which the retinal veins of the eyes appear "milky"
  • Eruptive xanthomas - small, yellowish bumps on the skin that contain fatty deposits 
  • Abdominal pain
  • Acute or recurrent episodes of pancreatitis - inflammation  of the pancreas
  • Blood that, when drawn, appears milky 

Acute pancreatitis is the most serious complication of FCS and can occur repeatedly. It can lead to long-term pancreatic dysfunction and may be fatal if untreated. Patients with FCS are at a higher risk of developing pancreatitis compared to individuals with high triglycerides from other causes. Thus, one of the main goals of treatment is to reduce this risk as much as possible. 

Diagnosis of FCS

FCS is diagnosed by a combination of clinical signs and symptoms, and extreme elevations in triglyceride levels. FCS should be suspected when the following are present:
  • A history of frequent episodes of acute pancreatitis 
  • Recurrent bouts of abdominal pain
  • Fasting triglycerides above 885 mg/dL on several occasions and likely to be treatment-refractory 
  • Absence of secondary causes for elevated triglycerides
  • Early-onset of symptoms (childhood, adolescence, or early adulthood)

If a physician suspects FCS, genetic testing can be performed to confirm the diagnosis. However, cost and access to genetic testing may limit its use.  Regardless of whether or not genetic testing is performed, appropriate management should be implemented when FCS is suspected.

Familial chylomicronemia syndrome (FCS)


Treatment of FCS

Management involves limiting daily fat intake to less than 15 to 20 grams (less than 10-15% of total daily calories). Avoidance of alcohol and simple, refined carbohydrates, such as those found in sodas and candy, are also very important for preventing further rises in triglycerides. Certain medications can also raise triglyceride levels. It is important to discuss your medications with your doctor to determine if any may need to be discontinued. If you have diabetes, it is important that it be well-controlled

Traditional medications used to lower triglycerides are often ineffective in patients with FCS. So far, no medications have been approved for treatment of FCS, specifically.

If you suspect that you or a loved one has FCS, find a physician who can diagnose you and help you understand FCS. This is the most important step you can take to receiving the appropriate care. FCS is rare and often misdiagnosed, so document your symptoms and share them with your provider. Learn about FCS by seeking patient resources and educating yourself and community about this condition.

Questions to Ask Your Healthcare Provider

  • How often should I have my blood triglyceride levels checked? 
  • What is the cause of my high triglyceride levels? 
  • What kind of changes do I need to make to my diet and exercise habits? 
  • Do I need to take medication? What kind? 
  • Does anyone in my family need to be tested for this problem? 

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