Illustration of a transformed lymphatic stem cell associated with the disease acute lymphoid leukaemia (ALL). ALL is a cancer of the lymphocytes caused by a genetic change in stem cells, allowing the release of many immature cells. These cells accumulate in the bone marrow and prevent the production of other blood cells such as red blood cells, platelets, and other white blood cells. Patients with ALL are more at risk for infection, anaemia, bruising, and blood loss.