There are many disorders of blood and bone marrow and they can be broadly divided into three groups
Some blood cancers develop and grow very slowly so they do not cause significant problems and require only blood count monitoring. These are termed chronic malignancies. Other blood cancers develop and progress rapidly and are very aggressive. These are termed acute malignancies.
Malignant haematological disorders include:
Leukaemia: cancer of the bone marrow.
Lymphoma: cancer of the lymph tissue, lymph nodes and spleen.
Multiple myeloma: cancer of plasma cells that usually produce antibodies.
Myelodysplastic syndrome: a group of blood cancers in which the bone marrow does not make enough healthy blood cells.
Myeloproliferative disorders: group of blood cancers in which the body makes too many blood cells.
This is a very large group of conditions of bone marrow and spleen that are not cancerous. They include inherited illnesses caused by faulty genes being passed from parents to children. Other benign blood diseases are acquired during the life, for example anaemia from low vitamin levels or autoimmune anaemia, where the body starts to attack it’s own blood cells.
Benign haematological disorders can affect:
red blood cells: the most common disorder is anaemia. Anaemia is a lack of red blood cells, a common sign of many diseases. Causes range from chronic bleeding due to gut diseases or heavy periods to longstanding infections or inflammation. Some anaemias are due to inborn errors of red cell production; some are acquired due to impaired regulation of the body’s immune defence systems. Red blood cells contain haemoglobin and this complex protein carries oxygen from the lungs to other tissues. Abnormalities of haemoglobin can cause many different disorders. They are nearly always inborn and are known as haemoglobinopathies.
white blood cells: the most common condition is low white cell count. This is a feature of many medical illnesses including viral infection, and autoimmune disorders. Two main types of white blood cells are lymphocytes (and low lymphocyte count is called leukopenia) and neutrophils (low neutrophil count is known as neutropenia). Investigation of low neutrophil counts can lead to discovery of other diseases or disorders, including some malignant haematological disorders. In most people this abnormality is only mild and does not cause any problems.
platelets: the most common abnormality is low platelet count known as thrombocytopenia. Low platelets can be a sign of many diseases including chronic infections and liver diseases. An impaired immune system can also cause immune thrombocytopenia (ITP), the most common reason for low platelets.
Problems with coagulation include:
Thrombosis: in these conditions the blood is more likely to clot, for example thrombophilia, factor V Leiden.
Bleeding: in these conditions clotting or platelet factors are low or do not work properly, for example haemophilia.