[Cytogenetic studies of Chilean children with acute lymphoblastic leukemia]. / Estudios citogenéticos en niños chilenos con leucemia linfoblástica aguda.

Acute lymphoblastic leukemia (ALL) is the most frequent childhood cancer. The leukemic cells of ALL patients show several well defined numeric and structural chromosomal abnormalities which are universally known for its prognostic implications. We studied a group of 44 children with ALL, to investigate the incidence of chromosome aberrations in ALL, its lymphocyte lineage and some clinical feature associations, and the finding of non previously described aberrations. A high proportion of patients (79.5%) showed chromosomal abnormalities. Most of them had a pseudodiploid karyotype (46 chromosomes), characterized mainly by a translocation. In relation to chromosome number, 27% of them were hyperdiploid with more than 50; 9% hyperdiploid between 47-50 and 7% hypodiploid (less than 46). Among structural aberrations found, were the following recurrent translocations: t (1; 19), t (4; 11), t (9; 22) in 6.8%, 9.1% and 2.3% of cases respectively, all related to an early B immunophenotype. Other translocations found, compromised regions 7q22, 9p21 - 24. Two new translocations in ALL were found: t (1; 5)(q23; q33), apparently balanced, and t (13; 21)(q14; q22), unbalanced. Other recurrent structural changes found were: deletion (6q), (7q), (9p), (11q), (12p), inversion (3q), isochromosome (7q), maker chromosomes and double minutes. The distribution of chromosome abnormalities in this group of patients was in agreement with previous reports from other investigators.

[Cytogenetic studies in myelodysplasias]. / Estudios citogeneticos en mielodisplasias.

Cytogenetic studies were performed in 29 patients with myelodysplasia, 12 males and 17 females with a mean age of 61 years. The distribution of patients according to FAB groups were as follows: refractory anemia (RA) 7, sideroblastic refractory anemia SRA) 6, refractory anemia with excess blasts (RAEB) 12 and refractory anemia with transformation excess blasts (RAEB-t) 4. Cytogenetic anomalies were found in 48% over all, 78% in patients with RAEB and RAEB-t forms and only 23% in patients with simpler forms of myelodysplasia. Multiple and complex chromosomal alterations were found in 50% of abnormal studies, only in patients with complex forms. In general, structural rearrangements and deletions were less frequent than numeric defects, with a slight preponderance of chromosomal losses. Alterations of chromosomes 5, 7, 28, 21, 22, 8, 11 and 15 were the most commonly observed. Survival was decreased from 60 months in patients with normal karyotype to 6 months in those with chromosomal alterations. Thus, chromosomal abnormalities are related to excess blasts and to survival in patients with myelodysplasia.