Lysosomal acid lipase deficiency (LAL deficiency or LAL-D) is an autosomal recessive inborn error of metabolism that results in the body not producing enough active lysosomal acid lipase (LAL) enzyme. This enzyme plays an important role in breaking down fatty material (cholesteryl esters and triglycerides) in the body. Infants, children and adults that have LAL deficiency experience a range of serious health problems. The lack of the LAL enzyme can lead to a build-up of fatty material in a number of body organs including the liver, spleen, gut, in the wall of blood vessels and other important organs.