The bone marrow is the spongy tissue inside the large bones in the body.
Myelodysplastic syndromes occur most often in older people, but they can occur in younger people.
The most common sign is anemia, which means there are too few mature red blood cells to carry oxygen. There may also be too few white blood cells in the blood to fight infections. If the number of platelets in the blood is lower than normal, this may cause people to bleed or bruise more easily. A doctor should be seen if a person bleeds without any reason, bruises more easily than normal, has an infection that won't go away, or feels tired all the time. If there are symptoms, a doctor may order blood tests to count the number of each kind of blood cell.