Adenine phosphoribosyltransferase (APRT) deficiency is an inherited disorder caused by mutations in the APRT gene. This gene provides instructions for making an enzyme called adenine phosphoribosyltransferase, which is involved in the breakdown of certain molecules called purines. Purines are components of DNA and RNA, which are the molecules that carry genetic information. Mutations in the APRT gene reduce or eliminate the activity of the adenine phosphoribosyltransferase enzyme, leading to a buildup of purines in the body. This buildup can cause kidney stones, gout, and other health problems.