Chronic myelogenous leukemia is the best known member of of a group of diseases called myeloproliferative diseases. It is characterized by a high WBC count, like most chronic leukemias. The WBC count usually exceeds 100 G/l at the time of diagnosis. Spenomegaly is very frequent. The disease starts as a slow chronic process, then after some time it turns into a so called blast crisis, which is actually an acute leukemia.
Examination of the peripheral blood smear is very useful. You will propably note the high number of WBCs first. An extreme left shift can be seen: all stages of the granulocyte development are present from myeloblast to segmented neutrophil, in a more or less even distribution. That is why this blood film gives an interesting, mixed and colorful impression, somewhat similar to that of the bone marrow. Basophilia is frequent, but eosinophilia can occur as well. You may see normoblasts as well in the peripheral blood, because of the anemia.
The GAPA or LAP (leukocyte alkaline phosphatase) should not be mixed up with alkaline phosphatase (ALP) activity, which is measured in serum. The ALP activity is increased most frequently in obstructive jaundice and in bone diseases. It is measured from serum with the usual technique used for other enzymes. On the other hand, GAPA is an intracellular enzyme activity, the alkaline phosphatase activity present within the leukocytes. Its determination is somewhat subjective: after performing the proper cytochemical reaction a person has to study 100 leukocytes in the smear, and assign a score (from 0 to 4) to every one of them. The sum of these scores will provide an indicator of intracellular activity of the enzyme (this is the so called GAPA score).
| The GAPA activity in CML is very low, the cells here are completely
negative. |
| The GAPA activity in CML is very low, the cells here are completely
negative. |
| Normal GAPA activity in a neutrophilic segment (normal peripheral blood).
The brown specks in the cytoplasm denote positivity.
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