Acquired X-chromosome aneuploidy in children with acute lymphoblastic leukemia

Background. A cytogenetic study of 75 consecutive children with ALL reveale d a normal karyotype, a low hyperdiploid karyotype (including 47-50 chromos omes), and a high hyperdiploid karyotype (including >50 chromosomes) in 10, 12, and 33 patients, respectively. An acquired extra X-chromosome was dete cted at diagnosis by conventional cytogenetics in 29 (88%) of 33 children w ith a high hyperdiploid karyotype and in 4 (33%) of 12 children with a low hyperdiploid karyotype. X-chromosome aneuploidy was retrospectively studied by fluorescence in situ hybridization (FISH) in eight and 20 patients with a normal and a hyperdiploid karyotype, respectively. Procedure. A classica l cytogenetic study was performed according to standard methods. FISH with the centromeric probe specific to X-chromosome was used to study interphase cells of bone marrow or blood samples. Results. An extra X-chromosome was found by FISH in all 13 patients with a high hyperdiploid or tetraploid, in 6 of 7 patients with a low hyperdiploid, and in none with a normal karyoty pe. Two children with a normal karyotype displayed monosomy X. Altogether, 57.3% of newly diagnosed children displayed X-chromosome aneuploidy. Conclu sions. Our study indicates that X-chromosome aneuploidy may be the most com mon chromosome abnormality in childhood ALL. It can be detected in nearly a il children with a high hyperdiploid karyotype and up to one-half of the pa tients with a low hyperdiploid karyotype. FISH with an X-chromosome centrom eric probe is a rapid and simple tool to detect an abnormal clone at diagno sis in the majority of children with ALL and is useful in confirming remiss ion in these patients. Med. Pediatr. Oncol. 32:360-365, 1999. (C) 1999 Wile y-Liss, Inc.