Every person starts out life as a single tiny cell. The information that tells the cell how to build a human body is stored in an encyclopedia of information known as the DNA. This encyclopedia is divided into thousands of short chapters, called genes. Each gene contains the information for building one tiny part of the body, like a piece of liver or muscle.

One tiny cell cannot direct the whole operation of building the whole human body. To accomplish this huge task, it copies its entire encyclopedia of DNA for each new cell it produces. Each new cell then focuses on one part of the encyclopedia and uses the information to assist in the building process. Sometimes the machines that copy the genes for new cells make mistakes. Other times, the genes are damaged for unknown reasons. When this happens, the new cells no longer have the right information in the DNA encylopedia to build the body correctly.

Lesch-Nyhan disease is one of many genetic diseases that occur because of an error in a single gene. In the case of Lesch-Nyhan disease, the gene is called hprt. Extensive research efforts have already uncovered many of the genetic errors, known as mutations, responsible for disease. A list of the known mutations can be found in the Research section.