Chylomicron retention disease (CMRD) is a rare inherited disorder that affects the body's ability to absorb dietary fats. It is caused by a mutation in the gene that encodes the enzyme lipoprotein lipase (LPL). People with CMRD are unable to break down chylomicrons, which are large particles of fat that are normally broken down by LPL. As a result, these particles accumulate in the bloodstream, leading to a variety of symptoms, including abdominal pain, diarrhea, and malabsorption of fat-soluble vitamins. Treatment typically involves a low-fat diet and supplementation with fat-soluble vitamins.