What are the genetic changes related to autoimmune lymphoproliferative syndrome ?
Mutations in the FAS gene cause ALPS in approximately 75 percent of affected individuals. The FAS gene provides instructions for making a protein involved in cell signaling that results in the self-destruction of cells (apoptosis).  When the immune system is turned on (activated) to fight an infection, large numbers of lymphocytes are produced. Normally, these lymphocytes undergo apoptosis when they are no longer required. FAS gene mutations result in an abnormal protein that interferes with apoptosis. Excess lymphocytes accumulate in the body's tissues and organs and often begin attacking them, leading to autoimmune disorders. Interference with apoptosis allows cells to multiply without control, leading to the lymphomas and other cancers that occur in people with this disorder.  ALPS may also be caused by mutations in additional genes, some of which have not been identified.