Isochromosomes in acute lymphoblastic leukaemia: i(21q) is a significant finding

Mary Martineau, Roslyn Clark, Dianna M. Farrell, Jacqueline M. Hawkins, Anthony V. Moorman, Lorna M. Secker-Walker

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33 Scopus citations


The incidence, type, and clonality of isochromosomes at diagnosis were investigated in acute lymphoblastic leukaemia (ALL). An isochromosome was detected in 50/1,035 (4.8%) of successfully karyotyped patients, 41/919 children (4.5%) and 9/116 adults (7.8%), who were diagnosed within a 5 year period. Isochromosomes of 21q with breakpoints in the short arm at p11 or in the long arm at q10 or q22 were identified in 15 patients (1.4%) associated with B-lineage immunophenotype, a white blood cell count (WBC) of < 10 x 109/litre, and pseudo- or low hyperdiploidy. Isochromosomes of 17q and 7q occurred in 13 (1.3%) and 9 (0.9%) patients, respectively, and were associated with high hyperdiploidy. Isochromosomes of 9q and 6p occurred in 6 (0.6%) and 5 (0.5%) patients, respectively, whereas i(Xp), i(Iq), and i(8q) occurred in I patient each. The isochromosome occurred as the sole abnormality in 4 patients [3 with i(21q) and I with i(7q)] and in the stemline, but with other chromosomal changes, in 35 patients. It was confined to a clonally evolved sideline in 11 patients. Isochromosomes occurred with established abnormalities in 7 patients: with t(1:19)-i(7q)/i(9q)/i(7q) and i(9q) each in 1 patient; with t(4:11)-i(7q)/i(17q) in 1 and 2 patients, respectively; and with t(9:22)-i(9q) in I patient. This study indicates that isochromosome formation can be an early chromosomal change and suggests that i(21q) occurs more frequently at diagnosis than has been previously suspected.

Original languageEnglish (US)
Pages (from-to)21-30
Number of pages10
JournalGenes Chromosomes and Cancer
Issue number1
StatePublished - Sep 1996
Externally publishedYes

ASJC Scopus subject areas

  • Genetics
  • Cancer Research


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