Isochromosome 21 and other chromosomal abnormalities in a patient with erythroleukaemia.

Cytogenetic analysis in a patient with erythroleukaemia revealed a hypodiploid cellular clone with several acquired karyotypic aberrations including an isochromosome for the long arm of chromosome 21 : 45,XY,-5,-7,-18,-19,-21, + 17, + i (21q)(qter leads to cen leads to qter), + mar1, + mar2. The markers probably include respectively the major part of chromosome 19 and most of the long arm of chromosome 7. These rearrangements and their potential significance are discussed.