5q- anomaly preceding acute myeloblastic leukemia with 53 chromosomes without chromosome 5 abnormality.

Partial deletion of the long arm of chromosome 5 (5q-) was found in a patient with a myeloid disorder. After treatment, hematologic parameters became normal, but acute myeloblastic leukemia occurred after 58 months. At that time, cytogenetic studies showed the presence of an abnormal clone with 53 chromosomes and without 5q-. This exceptional case suggests that the 5q- abnormality may precede the occurrence of an acute leukemia in favoring the appearance of unrelated malignant clones.