Myeloproliferative syndrome

Classification

The pathologies falling within the framework of myeloproliferative syndrome are (non-exhaustive list): Chronic myeloid leukemia. This pathology, in this group, finds a special place due to the latest discoveries, the diagnostic means implemented as well as its therapeutic management. This pathology is linked to a chromosomal anomaly called the Philadelphia chromosome. It consists of a translocation (a transposition of one segment of the chromosome onto another) between chromosome number 9 and chromosome number 22. This condition is characterized by a relatively significant increase in the number of neutrophilic granular cells, that is, cells that belong to the same lineage (variety) as certain white blood cells called neutrophils (in the bone marrow and blood). Chronic myeloid leukemia is often discovered by chance and begins insidiously with fatigue and weight loss. Its progression towards transformation into acute leukemia makes it serious. Palpation of the patient's abdomen shows isolated splenomegaly (increased spleen volume), but it is above all the data from the blood count (analysis of the number of red, white, and platelet cells) which show an often moderate anemia, i.e. around 10 grams per dl. Hyperleukocytosis (an increase in the number of white blood cells) is also observed. Bone marrow sampling reveals rich marrow with a large number of white blood cells and numerous megakaryocytes (platelet precursors) associated with a decrease in the number of erythroblasts (red blood cell precursors). The diagnosis of chronic myeloid leukemia is confirmed by studying the karyotype. The karyotype is the number of chromosomes contained in an individual's cells. This karyotype, carried out on bone marrow cells, highlights the Philadelphia chromosome. It also allows the identification of hybrid genes on this chromosome: the bcr-al-bl protein which is a diagnostic marker, that is to say a substance which, once measured, allows the exploration of a very specific and well-targeted disease. The treatment of chronic myeloid leukemia aims to suppress the progression towards the acute transformation phase. Previously, medical teams used the allograft technique (a transplant in which the graft is borrowed from a subject of the same species but with a different genetic makeup). Currently, other therapeutic possibilities are being used, particularly the use of alpha interferon, which allows for very long remissions, and also the use of STI 571 Gleevec (Imatinib Mesylate). This is the first anticancer drug in the "antityrosine kinase" family that inhibits the thyroskin kinase activity of the bcr-abl destruction protein (see above). Other hematological malignancies (blood disorders) that are part of the myeloproliferative syndrome include:

• Myelomonocytic leukemia
• Erythremia
• Myeloid splenomegaly with myelofibrosis
• Essential thrombocytopenia