Chylomicronemia

Chylomicronemia refers to a state of severe fasting hypertriglyceridemia caused by the accumulation of chylomicrons in the blood. It may be inherited (primary chylomicronemia) or arise secondary to other disorders or drugs. The condition is characterized by markedly elevated triglyceride levels and lipemic (milky) plasma.

Pathophysiology and causes

Normally, chylomicrons formed in the intestine are cleared by lipoprotein lipase (LPL) in the capillaries with the help of apolipoprotein C-II and other factors. Defects that impair LPL function or the proteins that enable chylomicron clearance (such as APOC2, GPIHBP1, APOA5) lead to excess chylomicrons and triglyceride elevations. Secondary causes include diabetes mellitus, alcohol use, obesity, hypothyroidism, and certain medications (such as estrogens and some antiretrovirals). In chylomicronemia, triglyceride levels commonly exceed 1000 mg/dL (11.3 mmol/L), and plasma may appear lipemic.

Clinical presentation and diagnosis

Patients may be asymptomatic or present with abdominal pain or pancreatitis related to very high triglycerides. Other signs can include eruptive xanthomas and lipemia retinalis in severe cases. Diagnosis relies on a fasting lipid profile showing marked triglyceride elevation with a predominance of chylomicrons on lipoprotein analysis. When a hereditary form is suspected, genetic testing and, in some cases, assessment of LPL activity or related protein genes can aid in differentiation.

Management

Management aims to reduce triglycerides and prevent pancreatitis. Strategies include dietary fat restriction and addressing secondary causes; very low-fat diets and, when appropriate, use of medium-chain triglycerides may be advised. Pharmacologic therapies such as fibrates or omega-3 fatty acids may lower triglycerides, though responses vary in genetic forms. In severe cases, plasmapheresis may be considered. Long-term care involves ongoing monitoring, lifestyle modification, and genetic counseling.