Leukemia, Chronic Myeloid

Alternative Names

  • CML
  • Leukemia, Chronic Myelogenous
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WHO-ICD-10 version:2010

Neoplasms

Malignant neoplasms

OMIM Number

608232

Mode of Inheritance

Unknown

Gene Map Locus

22q11.21

Description

Chronic Myeloid Leukemia (CML) is form of cancer affecting the blood cells, which is characterized by replacement of normal healthy blood cells by abnormally developed immature blast cells. Unlike the acute form of this disease, CML is a slow-growing cancer, and may take years to progress. The disease usually progresses through three distinct stages: the initial chronic phase (5% blast cells), characterized by an asymptomatic stage, the accelerated phase (15% blasts), which may last for months, and the blast crisis phase (30% blasts), in which the blasts may begin to form tumors outside of the bone marrow. The severity of the symptoms of the condition, including fever, fatigue, loss of appetite, night sweats, and abdominal pain, increase as the disease progresses from one phase to the next.

Diagnosis employs the techniques used in all forms of leukemia, including taking the Complete Blood Count, and bone biopsy. The finding of a Philadelphia chromosome in clinically suspected individuals is definitive diagnosis of the condition. CML can be managed either through chemotherapy, or bone marrow transplantation from a related donor. Interferon-alpha is one of the most relied drugs for chemotherapy. However, patients may not tolerate this drug very well, in which case, other drugs like hydroxyurea or busulfan may be administered. The most effective way to completely cure the disease however, is through bone marrow transplantation.

Molecular Genetics

More than 95% of patients with CML have a distinct chromosomal abnormality called the 'Philadelphia chromosome'. This abnormality involves a reciprocal translocation between chromosomes 9 and 22. The result of this translocation is the fusion of the Breakpoint Cluster Region (BCR) gene on chromosome 22 and the Ableson Leukemia Virus (ABL) gene on chromosome 9. The fusion product is the BCR-ABL gene, which codes for a protein with tyrosine kinase activity, capable of activating several signal transduction pathways within the cell, resulting in cancer.

Epidemiology in the Arab World

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Other Reports

Kuwait

Al-Bahar et al. (1994) studied the occurrence of leukemia subtypes in Kuwait between 1979 and 1989. CML occurred in 14.8% of a total of 723 cases; a rate similar to that reported in Western countries.

In 2009, Zamecnikova reported a rare coexistence of two translocations, t(16;16)(p13;q22), and the Philadelphia translocation, along with a deletion of the long arm of chromosome 7, in a single patient with chronic myeloid leukemia. Chemotherapy with imatinib mesylate led to the disappearance of the Ph-positive clones. However, the t(16;16) translocation and the del(7) abnormalities remained.

Oman

Ghosh et al. (1998) described acute graft versus host disease (GVHD) of the gastrointestinal tract in a patient with chronic myeloid leukemia after receiving an allogenic bone marrow transplant. The patient was diagnosed with chronic myeloid leukemia in chronic phase and had the Philadelphia chromosome with a three way translocation t(4,9,22). Initially, she was managed by hydroxyurea and then by alpha interferon. She then received bone marrow transplant from her complete HLA matched brother. Her stay in the BMT unit was complicated by Pseudomonas sp. Septicaemia, which was managed by antibiotics, and moderate veno-occlussive disease of the liver which was managed conservatively. At day 26, she was discharged home and advised to have pressure cooked food and bottled mineral water and to come for follow-up to receive cytomegalovirus prophylaxis. Mucoid diarrhea mixed with blood started on day 28 with low grade fever and tenesmus. The diarrhea became watery and greenish with flakes of mucous membrane floating in it within 24 hours. Blastocystis hominis was isolated from the stool (> five parasites/high power). Staph. Albus was grown from blood culture. She was started on Metronidazole, Ceftazidime and Vancomycin intravenously. On day 31, she was started on methylprednisolone as her diarrhea was worsening. Acute GVHD was confirmed by rectal biopsy as it showed crypt damage, apoptotic bodies and focal infiltration of the lamina propria by neutrophils. Blood investigations on day 32 showed blood count as follows: Hb of 11.5g/dl, WBC of 7.4, platelets of 158, absolute neutrophil count of 6.2, with 1% large granular lymphocytes seen in the smear. Liver function test revealed ALAT of 217 U/l, ASAT of 162 U/l, bilirubin of 45miromol/l, albumin of 22g/l, ALP of 328 U/l. Although her diarrhea improved after 3-4 days, her dysenteric symptoms continued till the disappearance of the parasite from stool on day 42, and Metronidazole was continued until day 46. After that no other pathogen was detected in her stool cultures and at follow-up, she had been seven months post BMT and off prednisolone and cyclosporine for three months with good graft function and no evidence of CML.

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Mubarak et al. (2002) described three patients with chronic myeloid leukemia (CML) in chronic phase who received interferon-alpha during pregnancy, starting from the 1st trimester. No maternal complications were reported and the three patients delivered normal looking babies apart from one baby who was found to have transient mild thrombocytopenia. Subsequently these children were followed for 30, 12, and 4 months and all had normal growth and development.

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