|LETTER TO EDITOR
|Year : 2014 | Volume
| Issue : 3 | Page : 383-384
Isodicentric Philadelphia [idic(Ph)] chromosome in a case of CML at chronic phase
BR Vundinti, L Kerketta, S Korgaonkar, S Vaidya, K Ghosh
Department of Cytogenetics, National Institute of Immunohaematology (ICMR), 13th Floor, New Multistoried Building, K. E. M Hospital Campus, Parel, Mumbai, Maharashtra, India
|Date of Web Publication||10-Dec-2014|
Dr. B R Vundinti
Department of Cytogenetics, National Institute of Immunohaematology (ICMR), 13th Floor, New Multistoried Building, K. E. M Hospital Campus, Parel, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Vundinti B R, Kerketta L, Korgaonkar S, Vaidya S, Ghosh K. Isodicentric Philadelphia [idic(Ph)] chromosome in a case of CML at chronic phase. Indian J Cancer 2014;51:383-4
|How to cite this URL:|
Vundinti B R, Kerketta L, Korgaonkar S, Vaidya S, Ghosh K. Isodicentric Philadelphia [idic(Ph)] chromosome in a case of CML at chronic phase. Indian J Cancer [serial online] 2014 [cited 2020 Feb 21];51:383-4. Available from: http://www.indianjcancer.com/text.asp?2014/51/3/383/146749
Chronic myelogenous leukemia (CML) is characterized by the translocation t(9;22)(q34;q11.2) i.e. Ph chromosome molecularly BCR/ABL fusion gene on the Ph chromosome. The isodicentricPh[idic(Ph)] chromosome is a rare chromosome aberration formed by the fusion of the two identical Ph chromosomes with retaining their centromeres. We describe the first case of CML in chronic phase with an idic(Ph) chromosome. A 32-year-old man was admitted to our hospital because of weakness and joint pains. He had no past history of antecedent hematological disorder. Physical examination of the patient revealed no alterations of the palpable lymph nodes and moderate hepatosplenomegaly and liver was enlarged 2 cm, the spleen 2 cm below the coastal margin. He had inconsistent bowel and bladder. Peripheral blood showed hemoglobin 11.7 g/dl, platelets 30 × 10 9 /L and white blood cells (WBC) 2.8 × 10 9 . Bone marrow aspiration showed 2% blast cells, erythroid series relatively reduced and showed delayed hemoglobinisation. Myeloid series showed marked hyperplasia. Megakaryocytes were increased with both mature and immature forms. The patient was diagnosed as CML at chronic phase and he was started on 400 mg imatinib mesylate therapy which was increased to 800 mg/day soon after initiating the therapy.
Chromosomal analysis at the time of diagnosis showed 46, XY, idicder(22) t(9;22)(q34;q11) (20)/46, XY  [Figure 1]a and b. The idic(Ph) chromosome had two centromeres and supposed to be generated by the fusion of two Ph chromosomes at the terminal regions of their long arms. Then the idic(Ph) chromosome was described as; 22pter→cen→ 22q11::9q34→9qter::9qter→9q34::22q11 →cen→ 22pter. Fluorescence in situ hybridization (FISH) with BCR/ABL dual fusion probe initially on metaphase spreads showed one larger BCR/ABL on idic(Ph) chromosome in all 10 metaphases examined [Figure 1]c. The FISH on interphase cells revealed BCR/ABL large signal in 90% of 200 interphase cells analyzed [Figure 1]d. The patient was followed up for two years an at six months intervals. The blood counts were high and cytogenetic investigation showed idic(Ph) positive. Hence, the patient was resistant to the therapy.
|Figure 1: (a) GTG-metaphase showing der (9) and idic(Ph) chromosomes. (b) Partial karyotype showing idic(Ph) chromosome break points. (c) FISH on metaphase showing large BCR-ABL fusion on idic(Ph) chromosome. (d) Interphase cell showing BCR-ABL fusion on isolated signal, which is idic(Ph)|
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The idic(Ph) chromosome was first reported in 1973 by Whang-Peng et al.  in late stage of disease in five patients who were initially classified as Ph positive. In our case idic (Ph) chromosome was detected at the time of diagnosis and to the best of our knowledge, this is the first case of CML patient with idic(Ph) at chronic phase. Overall 11 cases with idic(Ph) have been reported but all cases are at later stages or accelerated phase and associated with poor prognosis , . Yamato et al.  reported atypical idic(Ph) chromosome along with t(7;12)(q10;q10) in a case of ALL.
The isodicentric chromosomes can be heterogeneous in copy number, which leads to amplification and duplication of the hybrid BCR-ABL gene and such gene amplification and genomic heterogeneity is reported to be associated with drug resistance.The prognosis of CML patients with idic(Ph) is poorly understood. In the present case, response to standard chemotherapy was very poor and - complete remission was never achieved. However, the mean survival or the prognosis of CML cases with idic(Ph) chromosomes were not different from those of typical CML cases with single Ph chromosome. Szych et al.  reported idic(Ph) chromosomes in two imatinib mesylate resistant patients. In the present case idic(Ph) chromosome is probably causing resistance to therapy as patient's response to standard chemotherapy was poor and no complete remission was achieved after follow-up of two years. However, early detection may be helpful to the strategic treatment of such patients.
| » References|| |
Whang-Peng J, Knutsen TA, Lee EC. Dicentric Ph' Chromosome. J Natl Cancer Inst 1973;51:2009-12.
Kovacs G, Georgii A, Mainzer K. Three isodicentric Philadelphia chromosomes in acute phase of chronic myeloid leukemia: A case report. Cancer Genet Cytogenet 1986;20:29-33.
Pernice F, Squadrito G, Saitta A, Mazza G, Musolino C.Isodicentric Philadelphia chromosome in accelerated phase of chronic myeloid leukemia. Cancer Genet Cytogenet 1993;66:113-6.
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