RESUMEN
A total of 25 patients with primary myelodysplastic syndrome (p-MDS) were cytogenetically investigated. The incidence of abnormal karyotypes was higher, detected in 88 per cent of the patients and the most frequent abnormality was a terminal deletion of chromosome 7 (45% of the patients with abnormal karyotypes) followed by an i (17q) (18%), +21(14%), -5/5q (9%), del (11) (q22) (9%). Cytogenetic analysis after therapy/after leukaemic transformation indicated either stable clones (2 patients) or emergence of new clones such as inv(5) (q32q36), del (17) (p13), +20, +22 (1 patient each). It is to be noted that of the 8 patients with leukaemic transformation, 5 had del (7q). The leukaemic transformation (32% of the patients) was not related to the percentage of abnormal karyotypes not to the percentage of blasts at the time of the MDS presentation. Chromosome instability was shown by 10 (45%) patients. Our data indicate that higher frequency of chromosomal aberrations with involvement of chromosome 7 may be the result of underlying disease.