Historical Background Leukaemia
Leukaemia was first observed in 1845 by a pathologist Rudolf Virchow. He discovered an abnormally large number of white blood cells in a blood sample from a patient and term the condition leukaemie in German. Virchow coined the word leukaemia from two Greek words; leukos, meaning “White”, and aima, meaning “Blood”.
Ten years later Franz Ernst Christian Neumann, a pathologist found that one deceased leukaemia patient’s bone marrow was coloured “dirty green-yellow” instead of normal red and concluded that bone marrow deformity was responsible for the abnormal blood of leukaemia patients.
By 1900, leukaemia was viewed as a family of diseases as opposed to a single disease. By 1947, Sidney Farber, a Boston pathologist believed from the last experiments that aminopterin, a folic acid mimic, could potentially cure leukaemia in children. The majority with acute lymphoid leukaemia (ALL) who were tested showed signs of improvement in their bone marrow, but none of them were actually cured. This however, led to further experiments.
In 1962, researchers Emil J. Freireich Jr. and Emil Freilll used combination chemotherapy to attempt to cure leukaemia. The tests were successful with some patients surviving long after the tests.
As of August 2001, two out of three children treated via gene therapy recovered after one year of treatment. In 2000, approximately 256,000 children and adults around the world developed a form of leukaemia and 209,000 died from it.
This represents about 3% of the almost seven million deaths due to cancer that year, and about 0.35% of all deaths from any cause. Of the sixteen separate sites the body compared, leukaemia was the most common class of neoplastic disease and 11th most common cause of cancer related death.
In 2008, approximately 44,270 new cases of leukaemia were diagnosed in the United States. This represents 2.9% of all cancers in the U.S and 30.4% of all blood cancers.
EPIDEMIOLOGY : Historical Background Leukaemia
Leukaemia occur in both children and adults but most common in adults than children. More than 90% of all leukaemia are diagnosed in adults because cancer is much more common among adults hence 3% cancer diagnoses among adults are for leukaemias.
It is also more common in men than women, it has been described that 30% more men than women have leukaemia. Race has also been described as a risk factor, Histopanics, especially those under the age of 20 are at the highest risk for leukaemia, while caucassians (whites, Native Americans Asians, and Alaska Natives are at higher risk than Africans (blacks).
In leukaemias a clone of malignant cells may arise at any stage of maturation, that is the lymphoid, myeloid or pluripontential, stage. The etiology of this clonal expansion is poorly understood in most cases but it appears to involve some re-arrangement of DNA.
External factors, such as ionizing radiation, chemicals and alkylating drugs, and internal factors, such as chromosomal abnormalities, lead to DNA alterations.
Chromosomal re-arrangements may alter the structure or regulation of cellular oncogenes. For example, in the B-cell lymphocytic leukaemias, chromosomal translocations may put the genes that normally regulate heavy and light chain immunoglobulin synthesis next to the genes that regulate normal cellular activation and proliferation.
This results in proliferation of lymphoblasts. As the population of cells expands, the bone marrow starts to fail. Pancytopenia is typical and results in part from the physical replacement of normal marrow elements by the immature cells.
In addition, the abnormal cells may secrete factors that inhibit normal hematopoiesis. In chronic granulocytic leukaemia it involves characteristics chromosomal translocation called the Philadelphia chromosome (Ph).
As the bone marrow becomes replaced, the abnormal cells spill into the circulation and infilterate other organs, such as the liver, the eye, and the spleen. The ocular manifestations may be secondary to direct infilteration of the leukemic cells, as a result of abnormal systemic hematological parameters, opportunistic infections, or latrogenic complications arising from chemotherapy.
CLASSIFICATION OF LEUKAEMIA
Leukaemia is classified into four main kinds/categories based on clinical course; Acute and chronic (J. Ochei, 2000), and predominant cell type; Myeloid and lumphoid (Ezeilo, G.C., 2002). The former type some researchers viewed as traditional classification.Hence, we have Acute myeloid leukaemia (AML), Acute lymphoid leukaemia (CML) and chronic lymphoid leukaemia (CLL).
Acute leukaemia has a sudden onset and progresses rapidly and are fatal compared to the chronic leukaemia in which the reverse is the case. Within each of these four major kinds, exist several subcategories.
Other rare types of leukaemia include Hairy cell leukaemia (HCL), T-cell prolymphocytic leukaemia (T-PLL), large granular lymphocytic leukaemia and adult T-cell leukaemia.