Lipoprotein lipase deficiency (LPLD) is a rare genetic disorder that affects the body's ability to break down fats. It is caused by a mutation in the gene that codes for the enzyme lipoprotein lipase (LPL). This enzyme is responsible for breaking down triglycerides, a type of fat, into fatty acids and glycerol, which can then be used by the body for energy. People with LPLD have an inability to break down triglycerides, leading to an accumulation of fat in the blood and other tissues. Symptoms of LPLD can include abdominal pain, fatigue, and weight gain. Treatment typically involves dietary changes and medications to help reduce fat levels in the blood.