Autoimmune lymphoproliferative syndrome is a rare disease that affects both children and adults. Each of these three words helps describe the main features of this condition. The word autoimmune (self-immune) identifies ALPS as a disease of the immune system. The tools used to fight germs turn against our own cells and cause problems. The word lymphoproliferative describes the unusually large numbers of white blood cells (called lymphocytes (stored in the lymph nodes and spleens of people with ALPS. The word syndrome refers to the many common symptoms shared by ALPS patients.