From a clinical point of view and based on the speed of progression, leukemia is divided into acute (serious and sudden manifestation) o chronic (it slowly worsens over time).
Another important classification depends on the cells from which the neoplasm originates: we speak of lymphoid leukemia (or lymphocytic, lymphoblastic, lymphatic), when the tumor affects the intermediate precursors of T or B lymphocytes and myeloid leukemia (or myeloblastic, myelocytic, granulocytic), when, instead, the degeneration concerns the common progenitor of granulocytes, monocytes, erythrocytes and platelets.
Based on these considerations, we will have four common types of leukemia: chronic myeloid leukemia (CML) and acute myeloid leukemia (AML); chronic lymphocytic leukemia (CLL, also called lymphocytic) and acute lymphocytic leukemia (ALL, also called lymphoblastic).
Leukemia: what are the causes?
The causes of leukemia are not known, although it is now clear that the pathology, like other tumors, constitutes the final result of a complex series of events, which involve both constitutional genetic factors and environmental factors (ionizing radiation, toxic substances such as benzene derivatives, infectious agents…). The uncontrolled proliferation of leukemic cells is the result of a DNA anomaly, which – as in other types of neoplasia – determines an alteration of the mechanisms of regulation and control of cellular growth and differentiation. These processes are regulated by specific genes which, if damaged, can determine the transformation of a cell from normal to neoplastic, according to events that are only partially known.
Although the causes are not yet completely clear, some myelotoxic agents (benzene, alkylating agents and ionizing radiation) which can promote leukemogenesis have been identified with certainty.
The main risk factors, which can facilitate the onset of leukemic forms, are:
- Exposure to high doses of ionizing radiations, which can happen due to:
- Radiotherapy: the incidence is very high in subjects treated with radiotherapy for other tumors; in this case blood tumors are defined as secondary.
- Atomic accidents: worth remembering is the tragic toll among the survivors of the atomic explosions in Hiroshima and Nagasaki, exposed to high doses of radiation and seriously affected by leukemia.
- Professional exposure: it is possible that there is an association between leukemia and prolonged exposure to radiation, to some chemicals in the work and home environment, or to low frequency electromagnetic fields; however, there is still no definitive evidence demonstrating their close correlation.
- Benzene: used in the chemical industry, present in oil and petrol. Its prolonged inhalation over time is initially associated with haematological dyscrasia (alteration of the ratios of the elements that make up blood or other organic liquids), which can degenerate into leukemia. To exert a mutagenic and carcinogenic action, benzene must undergo oxidative conversion and transform into reactive intermediates that react covalently with DNA, causing interference with the replication and repair processes of the nucleic acid.
- The hiring of antiblastic, type II topoisomerase inhibitors and some chemotherapy drugs may increase the risk of secondary leukemia (especially in combination with radiotherapy). The drugs that induce greater susceptibility are: alkylating agents (chlorambucil, nitrosoureas, cyclophosphamide).
- To smoke it can contribute to the onset of some forms of leukemia (1/4 of all acute myeloid leukemias occur among smokers), due to the presence of some substances contained in cigarettes, such as benzopyrene, toxic aldehydes and certain heavy metals (example: cadmium and lead).
- Someone hereditary diseases – such as Down syndrome or chromosomal instability syndromes – are linked to a 10-20 times higher risk of developing leukemia in the first ten years of life. In some of these pathologies, the genetic mutation directly affects particular proteins involved in DNA repair processes. The risk of developing leukemia is therefore related to a lower cellular efficiency in the protection mechanisms in the event of genetic alterations.
- Myelodysplasia (preleukemic pathology) e other blood diseases predisposing: they make you more susceptible to the onset of acute myeloid leukemia.
- Human T-cell virus type 1 (HTLV-1): they are a class of oncogenic retroviruses (classified as oncoviruses), also called human T-cell leukemia viruses (Human T-cell Leukemia Virus), capable of causing, in rare cases, adult leukemia and lymphoma, and promoting cell proliferation indirectly: the virus replicates slowly and remains latent for a very long time in infected cells, mainly T lymphocytes. HTLV infection -1 is implicated in particular in chronic lymphoblastic leukemia (CLL).
- Family transmission: only in rare cases does a patient suffering from leukemia (chronic lymphatic leukemia, in particular) have a parent, sibling or child affected by the same disease.
Exposure to one or more risk factors potentially implicated in leukemogenesis does not necessarily cause the onset of the disease. Furthermore, it is essential to remember that specific events occur in the pathogenesis of different types of leukemia chromosomal alterationswhich allow us to characterize the different neoplastic forms, such as for example the translocation t(9;22)with formation of the Philadelphia chromosome, in chronic myeloid leukemia or la trisomy of chromosome 12, common in patients with chronic lymphocytic leukemia. During diagnosis, the identification of specific aberrations affecting genes and chromosomes, using conventional cytogenetic techniques, in situ hybridization or molecular biology, makes it possible to identify the leukemia subtype and guide towards the therapeutic choice.
Leukemia Symptoms: how does it manifest itself?
The disorders and symptoms of leukemia can vary in each patient, based on the type and quantity of tumor cells, and the severity of the disease. In some cases, in the initial stages the symptoms may be non-specific and could be caused by other concomitant diseases.
Due to the proliferative advantage of leukemic cells, a clonal expansion occurs that occupies a large part of the bone marrow and spills into the bloodstream. The invasive nature of neoplastic clones also allows their spread to the lymphatic glands or other organs (example: spleen) and can cause swelling or pain in various parts of the body.
Patients suffering from chronic leukemia may be asymptomatic and the doctor can detect clinical signs during a routine blood test, while patients with an acute form of the disease often undergo a medical examination due to a feeling general malaise.
Therefore, i general symptoms that can develop include:
Symptoms caused by blast infiltration into the bone marrow:
Symptoms of leukemia caused by infiltration into other organs and/or tissues:
In advanced stages, accentuation of the above symptoms may occur and the clinical manifestations of leukemia may include:
If symptoms such as high fever, sudden bleeding or convulsions occur without an apparent cause, emergency treatment for acute leukemia is essential.
If during the disease remission phase (attenuation or disappearance of the symptoms of an illness) there are signs of recurrence, such as an infection or haemorrhage, it is necessary to undergo a medical check-up.
How common is Leukemia?
The pathology tends to manifest itself in the first decade of age, as regards acute leukemia, while the chronic forms mostly affect adults and develop especially after the age of 40, with greater frequency in relation to increasing age. Acute leukemia, in particular, accounts for 25% of all cancers in children.
The overall incidence is approximately 15 people per 100,000 each year.
Other articles on ‘Leukemia – Causes, Symptoms, Epidemiology’
- Leukemia: Diagnosis
- Leukemia: Cure and Treatment
- Leukemia – Stem Cell Transplant and Bone Marrow Transplant
- Therapies for the various types of leukemia
- Side Effects of Leukemia Treatments