Familial chylomicronemia syndrome (FCS) is a genetic disease in which there is a build-up of chylomicrons, or large lipoprotein particles, which transport dietary fat and cholesterol throughout the body.
Under normal circumstances, lipoprotein lipase (LPLase) breaks down chylomicrons in the blood, but in patients with FCS, LPLase does not function properly. Therefore, patients are unable to break down chylomicrons, which leads to increased triglyceride levels.
Normal triglyceride levels are <150 mg/dL or 1.7 mmol/L. In FCS, triglyceride levels may increase to 10 times that concentration.
The key to managing patients with FCS is recognizing the symptoms of this often well-hidden disease so they can be managed properly. Recurrent pancreatitis is a main concern.
Signs and Symptoms
Symptoms vary greatly among patients, but often includefatigue, impaired cognition, and numbness or tingling sensations. In more severe instances, eruptive xanthoma, lipaemia retinalis, abdominal pain, and hepatosplenomegaly may occur. In many cases, it is not until these latter symptoms present that a clinician is led to suspect a rare condition and pursue a proper diagnosis.
For persons who go undiagnosed until adulthood, the first hint that they have FCS is when they develop pancreatitis after entering college, where alcohol and fatty foods are often consumed. A diagnosis is usually made following a blood sample showing 1) extremely high triglyceride levels that do not respond to standard therapies and 2) a cloudy serum sample due to the presence of chylomicrons.
There is currently no FDA-approved treatment for FCS. In 2014, Europe approved Glybera, the first (and only) gene therapy ever approved that was intended for FCS treatment. Uniquire, the company that developed the drug, wasn’t able to properly monetize it, however, nor could they keep abreast of the regulatory processes in place for this new type of treatment. This year, the company stopped producing the gene therapy, and it was reported that they had only been able to sell 1 dose since its approval. The price tag for the gene therapy was said to be approximately $1 million, which may seem high, but it should be noted that the therapy is for an ultra rare condition (1 in 1 million people) and a patient only needs the treatment once to be cured.
Current management for FCS is a strict, life-long diet. Patients usually work with a registered dietician who can help them establish healthy dietary habits, such as consuming extremely low amounts of fats and simple carbohydrates. The restrictions also limit total carbohydrates, eliminate alcohol, and meet requirements for essential fatty acids and other nutrients.
Medium chain triglyceride (MCT) oil may be helpful for these patients. Obtained by prescription, it is a safe source of fats and calories for patients with FCS. When consumed, MCTs are rapidly hydrolyzed and removed through the portal circulation.
There is currently 1 orphan drug in development. Volanesorsen is designed to reduce the amount of apoC-III in the bloodstream. ApoC-III is a protein that regulates triglycerides and reduces the amount of apoC-III in the blood. In a recent clinical study of 67 patients with FCS, volanesorsen treatment reduced triglycerides an average of 70%. A phase 3 study is currently underway.
The main advocacy group for FCS patients is the FCS Foundation, which provides resources with links to clinical trials.