Familial chylomicronaemia symdrome (FCS)

What is familial chylomicronaemia syndrome (FCS)?

Familial chylomicronaemia syndrome (FCS) is the name for a group of rare genetic disorders that cause very high levels of triglycerides in the blood.

Triglycerides are a kind of fat, and high levels of triglycerides can lead to serious health problems in the long term, including pancreatitis and diabetes. With a very low fat diet, you can help to avoid these problems. 

You might also hear FCS called lipoprotein lipase deficiency (LPLD) – which is the most common type of FCS – or chylomicronaemia.

FCS is very rare, around one to two in a million people have it.

If you have FCS, you have it from the time you’re born, but when the symptoms appear and how much they affect you varies from person to person. For some, symptoms are more severe and appear in  infancy or early childhood and they will usually be diagnosed at a young age. For others, symptoms appear in childhood or adolescence, and they will be diagnosed later. 

Learn about other inherited (genetic) cholesterol conditions

Learn more

What are the symptoms of FCS? 

  • Regular bouts of pain in the abdomen (stomach area) – this can be mild or severe.
  • Pain in the joints.
  • Small, raised, fat-filled spots on the skin (called eruptive xanthomata) – these often appear on the buttocks, knees and arms, and improve when triglyceride levels are lowered.
  • Fatty stools (known as steatorrhoea) – which appear pale and oily in appearance, and are difficult to flush.
  • Pale pink arteries and veins in the retina of the eye (called lipaemia retinalis) – which can be spotted by opthalmologists (eye specialists) on eye tests.
  • Sudden (acute) pancreatitis – which causes pain and swelling around your stomach, feeling and being sick, fever or chills, and jaundice (yellowing of the eyes and skin). This can be very serious. 
  • Enlarged liver or spleen – which causes pain.   
  • Extreme tiredness (known as fatigue) – you might also have fatigue after a meal. 
  • Problems with memory and concentration. 
  • Low mood (depression) – which could be caused by a lack of energy, recurring symptoms and the challenges of eating a restrictive diet to manage FCS. 

What are the long-term effects of FCS? 


The pancreas is a vital organ. It makes some of the enzymes needed for digestion, and the hormones insulin and glucagon which control your blood sugar levels.

FCS causes episodes of pancreatitis, where the pancreas becomes inflamed and swollen. Acute pancreatitis (when it comes on suddenly) can be very serious or even life-threatening and needs urgent treatment in hospital.

Repeated attacks of acute pancreatitis can lead to chronic (long term) pancreatitis and can cause permanent damage.  


If you have FCS, you’re more likely to develop Type 2 diabetes, where your blood sugar levels aren’t properly controlled and rise too high. Diabetes is more likely if you have repeated bouts of pancreatitis because this can damage the pancreas and it can no longer produce the hormones which control blood sugar.  

Diabetes can lead to a number of serious health problems including heart disease and kidney disease.

If you develop diabetes your doctor will want to keep your blood sugar levels well controlled, for example with medicines such as Metformin, sitagliptin and insulin.

How does FCS raise your triglycerides?

Most people have an enzyme (a type of protein) called lipoprotein lipase in their bodies. It clears triglycerides from their blood after a meal.

If you have FCS, you are missing this enzyme, or you have a very small amount and it might not work properly. Without lipoprotein lipase, fat can’t be cleared from your blood and your triglyceride levels stay high. This makes the blood appear creamy white.  

What does Chylomicronaemia mean?

Triglycerides in the blood are packaged into balls called chylomicrons. So, the ‘Chylomicronaemia’ part of the name Familial Chylomicronaemia Syndrome simply means there are too many chylomicrons in the blood. In other words, there’s too much fat.

What causes FCS?

FCS is passed down in the genes
The ‘Familial’ part of Familial Chylomicronaemia Syndrome means the condition is passed down through families. It’s genetic.

There are five different genes known to be involved in FCS – a fault in any of these can cause FCS.

We have two copies of every gene – one from each parent. Both copies of a gene involved in FCS need to be faulty for you to inherit it. This is known as 'autosomal recessive'. 

If you only have one faulty copy of a gene, you won’t have FCS but you will be a carrier
Carriers don’t have FCS or its symptoms, but might have slightly higher blood fats and therefore a slightly higher risk of heart disease. There are tests to find out if you are a carrier.

If you have FCS, you will pass on a faulty gene to any children you have, so they will be a carrier
They will only have FCS if they also inherit a faulty gene from the other parent. 

See how FCS is diagnosed and treated


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