Lysosomal acid lipase (LAL), with 378-amino acid protein( 43-54 kDa), functions in the lysosome to catalyze the hydrolysis of cholesteryl esters and triglycerides which are taken up by receptor-mediated endocytosis. An inherited deficiency or low activity of human lysosomal acid lipase results in the intralysosomal storage of the respective lipid substrates. So it is also responsible for the rare conditions of Wolman disease and cholesteryl ester storage disease (CESD). As the enzyme is synthesized by all nucleated cells, lipid-laden cells are found in all organs, particularly in liver, spleen, the adrenal and the hemopoietic system, and in the intestine as well as in the lymph nodes, lungs, testes, and ovaries.