Bone marrow is the spongy tissue inside some of your bones, such as your hip and thigh bones. It contains immature cells, called 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.

If you have a bone marrow disease, there are problems with the stem cells or how they develop. Leukemia is a cancer in which the bone marrow produces abnormal white blood cells. With aplastic anemia, the bone marrow doesn't make red blood cells. Other diseases, such as lymphoma, can spread into the bone marrow and affect the production of blood cells. Other causes of bone marrow disorders include your genetic makeup and environmental factors.

Symptoms of bone marrow diseases vary. Treatments depend on the disorder and how severe it is. They might involve medicines, blood transfusions or a bone marrow transplant.