Bone marrow is the spongy tissue inside some of your bones, such as your hip and thigh bones. It contains stem cells. The stem cells can develop into the red blood cells that carry oxygen through your body, the white blood cells that fight infections, and the platelets that help with blood clotting. Causes of bone marrow diseases include genetics and environmental factors. Tests for bone marrow diseases include blood and bone marrow tests. Treatments depend on the disorder and how severe it is. They might involve medicines, blood transfusions or a bone marrow transplant.