Leukemias are cancers characterized by abnormalities of white blood cell precursors in the bone marrow, with or without the presence in blood of abnormal cells.
Process in AT
The bone marrow is the site of production of all blood cells from stem cells:
- Red cells
- Precursors of white blood cells (different types of "babies" white blood cells that take their final function elsewhere).
Some external factors are recognized as potential causes of development of leukemia. Among the main, we find:
- Radiation (X-rays, radioactivity ...)
- Chemicals (pesticides, fertilizers, benzene ...)
- Some medical treatments like chemotherapy and radiotherapy for an earlier and cancer.
But even if they do not constitutent the majority of cases of leukemia, we know that these factors generate DNA breaks in cells and in people with AT and the absence of ATM protein allows these abnormal cells to reproduce. This transformation mechanism is certainly highly contributory to the fact that these patients are prone to leukemia.
- Low platelets: bleeding
- Decrease of red blood cells: anemia, paleness, palpitations
- Decrease of white blood cells with an immediate impact on the immune system: repeated serious infections
- Fever, headache, and sometimes paralysis
We are talking about:
- Lymphocytic leukemia when the babies white cells involved were designed to give lymphocytes(B and T cells, see Immune system")
- Myeloid leukemia for the other cell lines
- Acute leukemia if the abnormality involves immature white blood cell precursors. In this case, the proliferation of cells is very rapid, leading rapidly to the onset of clinical signs of the disease
- Chronic leukemia if the abnormality does not affect the differentiation of precursors that can still differentiate into mature cells but whose function is abnormal. Typically, the symptoms may be delayed and evolution may be more indolent in the beginning.
Leukemia or lymphoma?
It may be noticed finally that the boundary between lymphoma and leukemia is not always very marked: in some non-Hodgkin's lymphoma, cells may be present in blood and certain aggressive lymphomas (lymphoblastic or Burkitt's lymphoma) may present an affected bone marrow and treated on a common treatment program to lymphomas and leukemias. Conversely, chronic lymphocytic leukemia are sometimes classified as lymphoma ... not easy to sort things out.
The mechanisms of malignant transformation are very similar and the main difference may be summarized as follows:
- acute leukemia (lymphoblastic): abnormality leading to blockage of maturation and abnormal accumulation by overgrowth of lymphocytes precursors that invade the bone marrow, hindering its functioning(reduction of other normal blood cells, red cells, unaffected white cells and platelets ) and sometimes also present in the circulating blood.
- chronic lymphocytic leukemia and non-Hodgkin lymphoma: abnormality leading to the accumulation of abnormal lymphocytes (usually B) but without abnormal differentiation. In chronic lymphocytic leukemia, accumulation occurs primarily in bone marrow and lymph nodes and abnormal lymphocytes are present in excess in the circulating blood. The normal bone marrow functioning is obstructed very late in the evolution that is generally very slow (lazy). In non-Hodgkin lymphoma accumulation is mainly in the lymph (and sometimes other organs) and more rarely in the bone marrow (and in this case abnormal cells can also be observed in blood but as a rule generally in small amounts).
Children with AT are predisposed to acute lymphoblastic leukemia and chromosomal abnormalities on chromosome 14 are frequently observed (see Laboratory and Immunity and AT). The treatment of acute leukemia will be to destroy the degenerated cells by chemotherapy fairly strong. But this does not happen without collateral damage and the need to replenish a capital of healthy cells in the bone marrow may pass through a bone marrow transplant.
Generally speaking, treatments have results that are improving and can treat between 70 and 80% of patients. The problem in AT being the patient's hypersensitivity to chemotherapy, it is necessary to adapt the treatments, but conclusive results can be obtained. Non-Hodgkin lymphoma and Hodgkin's disease can be also treated with diverse but usually lighter chemotherapy often possible in day hospital. Sometimes, radiotherapy (radiation) is associated.