by Nicole Evans M.D.

Created on: August 24, 2009   Last Updated: October 25, 2009

The most common acute leukemias are Acute Myelocytic Leukemia and Acute Lymphocytic Leukemia. There are several risk factors associated with the development of acute leukemia including:

-ionizing radiation exposure

-chemical carcinogens

-genetic translocations

-benzene exposure

-genetic disorders such as Down's syndrome

Acute leukemia occurs when progenitor blood cells transform into malignant cells and accumulate in the bone marrow. These malignant blood cells then disrupt the maturation process of normal cells that should be occurring in the bone marrow.

A bone marrow biopsy showing more than 30% immature cells will confirm the diagnosis of both suspected acute myelocytic leukemia or acute lymphocytic leukemia. The two cancers are differentiated from each other as described below.

Acute myelocytic leukemia (AML:

AML is more common in adults. Symptoms of AML include:

-fatigue, hemorrhage or bruising in 30% of patients

-infections of the lung and or skin in 25% of patients

-splenomegaly (enlarged spleen), hepatomegaly (enlarged liver) and lymphadenopathy in less than 25% of patients

AML is diagnosed by an elevated white blood cell count, the presence of blasts (early blood cells) in peripheral blood, a decreased absolute neutrophil count, a decreased hematocrit, and a decreased platelet count. Auer rods may be seen on microscopy in 10% of patients and will stain positively with Sudan black and myeloperoxidase.

There are subtypes of AML based on morphology. Subtype M3 is associated with disseminated intravascular coagulation (DIC). Subtype M5 is associated with gingival hyperplasia in 50% of patients.

The treatment of AML consists of chemotherapy. About 50 to 805 of patients will acheive remission following induction chemotherapy. The chemotherapeutic agent cytarabine and an anthracycline such as daunorubicin are often used. Those persons who do not enter remission with chemotherapy may undergo stem cell transplantation.

When considered the optimal treatment regimen it is beneficial to know the AML subtype. The M3 subtype, mentioned above for its association with DIC, responds very well to all-trans-retinoic acid in addition to the other chemotherapeutic agents.

ALL:

Acute lymphocytic leukemia (ALL) primarily affects children, although ALL does account for 20% of adult leukemia. There are three subtypes of ALL: L1, L2 and L3. The L2 subtype is associated is the type associated with adult cases.

Symptoms of ALL are abrupt in onset and often begin only a few weeks before the disease is diagnosed. These symptoms include:

-malaise

-fever

-lethargy

-weight loss

-bone pain

-infection

-hemorrhage.

In about 50% of ALL cases lymphadenopathy, splenomegaly and hepatomegaly will occur.

The diagnosis of ALL relies on an elevated leukocyte count, blasts in the peripheral blood, a decreased absolute neutrophil count, decreased hematocrit, and decreased platelet count. These diagnostic criteria are similar to AML, however Auer rods do not occur in ALL. Additionally, the L1 and L2 subtypes can be identified by the fact that the cells react positively with periodic acid-schiff (PAS) staining.

Patients with ALL may be treated with induction chemotherapy including vincristine, prednisone, daunorubicin, l-asparginase and cyclophosphamide. Most invidividuals with acute lymphocytic leukemia require low-dose maintenance chemo once they are in remission. However, some patients will end up requiring bone marrow transplantation.

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