Classification (On the Course of Disease):
Based on the course of disease, leukaemias are classified as acute and chronic.
It is a sudden onset, generally occurs in children under 14 years of age. It is associated with normocytic, normochromic anaemia, with decreased platelet count. Bleeding time is prolonged and white blood cell count may increase upto 1 lakh cells/cu mm. Immature and blast cells are present in peripheral blood smear. Acute leukaemia is rapid progressive disease.
It is slow progressive disease, anaemia may occur at later stages. White cell count is markedly increased and may go upto 9 lakhs /cu mm. Blast cells are seen occasionally.
In between these two, subacute leukaemia is also found in some cases. It is quite similar to acute leukaemia. But the total leucocyte count may be normal, decreased or increased upto 50,000.
Classification (On the Basis of Cell of Origin):
Leukaemias are further classified on the basis of the cell of origin, i.e. whether myelocytic or lymphocytic as:
1. Acute Myelocytic Leukaemia (AML)
2. Acute Lymphocytic Leukaemia (ALL)
3. Chronic Myelocytic Leukaemia (CML)
4. Chronic Lymphocytic Leukaemia (CLL)
Acute Myelocytic Leukaemia (AML):
Acute myelocytic leukaemia (AML) occurs in all age groups but more common in adults than in children. It is also called as acute granulocytic leukaemia (AGL). It is characterized by the presence of large number of myeloblasts in the bone marrow and their appearance in the peripheral blood.
Myeloblasts in the peripheral blood may vary from few to as much as 95%. Many variants of AMC have been described depending upon the type of cell predominating in the peripheral blood. These could be myeloblasts, promyelocytes, monoblasts or blasts of both myeloid and erythroid series.
In AMC, there is often inflammation of the gums, skin involvement, rectal ulceration, face tumor is observed. It is generally associated with normochromic normocytic anaemia AML is rapidly fatal with most patients dying from hemorrhage or infection due to bone marrow failure.
Acute Lymphoblastic Leukaemia (ALL):
Acute lymphoblastic leukaemia is more common in children than in adults, that too in males than in females. It is less sever than AMC and in many cases it is cured by intensive and sustained treatment.
ALL is the malignancy of the cells of lymphocytic series and it is characterized by the presence of increased number of lymphoblasts in bone marrow as well as in peripheral blood smear.
Bone pain, fever, bleeding, purpura, thrombosis, lymphadenopathy and central nervous system involvement is common in ALL. To differentiate between the diagnosis of AML and ALL, several special cytochemical stains and immunological markers can be used.
Chronic Myelocytic Leukaemia:
CML is also called as chronic granulocytic leukaemia (CGL). It is common in middle age group. It is characterized by the presence of marked increase in the cells of myelocytic series. The predominant cells are neutrophilic myelocytes and metamyelocytes. Total leucocyte count is generally higher than 50,000/ ?L to 2000, 000/ ?L.
Symptoms due to hypermetabolism are common in chronic myelocytic leukaemia. Anaemia is normocytic normochromic. Platelet count is usually increased. The abnormal Philadelphia (Ph) chromosome is present in the leukaemic cells of more than 95% of patients with CML. CML may develops into AML at later stages.
Chronic Lymphoblastic Leukaemia (CLL):
CLL is more often found in older persons (over 60 year) with men affected than women. It is characterized by marked increase of mature lymphocytes (above 15,000 cells/ ?L). The cell count may go very high and 80 to 90% of the cell look like immature lymphocytes. Prognostically, patients of CLL may live for many years without treatment.
Onset of this disease is slow and in early stages asymptomatic. Most patients have weight loss, and develop lymphadenopathy. In later stages of CLL, neutropenia, thrombocytopenia and the loss of normal functioning lymphocytes lead to inadequate immune responses resulting in various infections. Anaemia also develops in last stage.
i. Patient will die quickly (weeks-months) without treatment
ii. Associated with very immature, undifferentiated cells, little mature and therefore normal function and some intermediate maturation
iii. > 30% blasts in the bone marrow.
a. Without treatment it may be months or years before death
b. Mature and immature cells present
c. < 30% blasts in the bone marrow.