Familial lipoprotein lipase deficiency (FCS): symptoms, pancreatitis risk and diet

HEART UK explains that familial chylomicronaemia syndrome (FCS) is the name for a group of rare genetic disorders that cause very high levels of triglycerides, a kind of fat, in the blood. Lipoprotein lipase deficiency (LPLD) is the most common type. Most people have an enzyme called lipoprotein lipase that clears triglycerides from the blood after a meal. In FCS the enzyme is missing, or there is very little and it may not work properly, so fat cannot be cleared and triglyceride levels stay high, which can make the blood look creamy white.

The word chylomicronaemia refers to chylomicrons, the balls in which triglycerides are packaged in the blood. Too many chylomicrons means too much fat in the blood. This is different from the more common high cholesterol or the milder raised triglycerides seen with diet, alcohol or diabetes.

FCS is passed down in genes. HEART UK says five genes are known to be involved and that a change in any of them can cause FCS. Both copies of a gene must be altered for someone to inherit it, which is described as autosomal recessive. People with only one altered copy are carriers: they do not have FCS but might have slightly higher blood fats and a slightly higher risk of heart disease. Tests can find out if you are a carrier.

If you have FCS you will pass an altered gene to any children, who will be carriers, and they will only have FCS if they also inherit an altered gene from the other parent.

HEART UK says that when symptoms appear, and how much they affect you, varies. For some they are severe and start in infancy or early childhood, and for others they appear in childhood or adolescence. It lists:

• regular bouts of abdominal pain, mild or severe

• pain in the joints

• small, raised, fat-filled spots on the skin (eruptive xanthomata), often on the buttocks, knees and arms, which improve when triglycerides are lowered

• pale, oily stools (steatorrhoea) that are difficult to flush

• pale pink arteries and veins in the retina (lipaemia retinalis), which eye specialists can spot

• sudden (acute) pancreatitis

• an enlarged liver or spleen, which causes pain

• extreme tiredness, problems with memory and concentration, and low mood

The pancreas makes digestive enzymes and the hormones insulin and glucagon. HEART UK says FCS causes episodes of pancreatitis, in which it becomes inflamed and swollen, that acute pancreatitis can be very serious or even life-threatening and needs urgent hospital treatment, and that repeated attacks can lead to chronic pancreatitis and permanent damage.

The NHS says the main symptom of acute pancreatitis is tummy pain, which may start suddenly, be severe, affect the upper tummy, spread to the sides and back, feel worse after eating and feel better when leaning forward. It may be accompanied by a high temperature and nausea or vomiting. The NHS advises asking for an urgent GP appointment or calling NHS 111 for sudden severe tummy pain that does not go away or keeps coming back, or with a high temperature. Call 999 or go to A&E if the pain spreads to your back, you have persistent bloating, a fast heartbeat or breathing difficulty.

Most people with acute pancreatitis start to get better within a week and leave hospital in 5 to 10 days, according to the NHS, though it can be longer if it is severe. HEART UK notes that people with FCS will often have episodes of pain and pancreatitis throughout their lives even if they stick to a low-fat diet, and these can come on without warning.

HEART UK says that people with FCS are more likely to develop type 2 diabetes, particularly after repeated bouts of pancreatitis that can damage the pancreas so it no longer produces the hormones that control blood sugar. Diabetes can in turn lead to heart disease and kidney disease, so blood sugar is closely monitored and treated if it rises.

HEART UK says FCS can be diagnosed with blood samples, which may look creamy when triglycerides are very high, and that levels are usually over about 10 mmol/litre. Increasingly genetic tests are used, looking for changes in the genes that code for lipoprotein lipase and the proteins that work with it.

Most people are diagnosed as babies or young children, before the age of 10, because of tummy pain, pancreatitis and fat-filled skin spots. For others symptoms appear later, and they are diagnosed in their 20s, 30s and 40s. Some women show symptoms only in pregnancy, when blood fats rise naturally and rise even higher in FCS. Because it is so rare, some people are not diagnosed until they are teenagers or adults, and some are misdiagnosed.

HEART UK says the main treatment for FCS is a very low-fat diet, with limited simple sugars and refined carbohydrates, and low in alcohol. This stops triglycerides in the blood rising. A low-fat diet keeps the chances of pain and pancreatitis as low as possible, though it can be challenging because food is central to social life.

The medicines usually used to lower blood fats, such as statins and fibrates, do not help with FCS because they rely on lipoprotein lipase working properly. HEART UK says some medicines are available but have only a small effect, and describes volanesorsen as a newer injected treatment used alongside a very low-fat diet. It also advises avoiding smoking, which raises triglycerides and lowers HDL cholesterol, and being active for at least 150 minutes a week.

HEART UK recommends working with your specialist doctor, because most consultants will only ever see a few people with FCS. Support from a dietitian is an important part of care.

Because FCS is so rare, care is usually through NHS specialist lipid or metabolic services and a hospital pancreatitis pathway for emergencies. HEART UK says only around 55 to 110 people in England have it, so specialist knowledge is concentrated in a few centres. A private consultant can offer a second opinion, but ongoing monitoring, genetic testing and emergency care usually run through the NHS. Keep a written summary of your diagnosis so any emergency team can see it quickly.