A rare inherited disorder of cholesterol regulation where a deficiency of a transport molecule (cholesteryl ester transfer protein) results in cholesterol level abnormalities. The transport protein moves cholesterol from HDL molecules to other lipoproteins and hence regulates the size of HDL particles and plasma levels of HDL cholesterol. There is disagreement as to whether the condition increases, decreases or has no effect on the risk of coronary heart disease. See also Cholesteryl ester transfer protein deficiency