[Application of the high resolution chromosomic technic in patients in high risk of cytogenetic anomalies]. / Aplicación de la técnica de Alta Resolución Cromosómica en pacientes con alto riesgo para anomalías citogenéticas.

Since the beginning of cytogenetics, there has been a constant improvement of chromosomal culture and banding techniques. In 1976, Yunis described a high chromosomal resolution technique (HRC), that permits the detection of subtle chromosomal abnormalities. The present work, reports the results obtained when HRC was applied to the study of chromosomal abnormalities in patients with high risk of such. The study comprised 434 specimens of venous blood and 182 bone marrow aspirates. The samples were classified according to the presuntive diagnoses. The highest frequency of chromosomal abnormalities, was found in blood samples from patients with physical deformities with or without mental retardation (22.22%), followed by mental retardation autism and/or fragile X chromosome (13.66%), and in couples with reproductive disorders (5.8%). In bone marrow, the most frequent abnormalities corresponded to patients with chronic myeloid leukemia (78.43%), acute lymphocytic leukemia (62.10%), acute myeloide leukemia (61.9%), myelodisplastic syndromes (43.7%) and chronic lymphocytic leukemia (14.2%). The present results stress the need to apply the HRC technique when the probability of minute chromosomal abnormalities is high.

[Significance of chromosome changes in chronic myeloid leukemia]. / Importancia de las alteraciones cromosómicas en la leucemia mieloide crónica.

Chronic myelocytic leukemia is a particular subtype of leukemia characterized by increased myeloid precursor cells. It has been associated with the presence of the Philadelphia chromosome, described by Nowel and Hungerford in 1960, as a deletion of part of the long arm of a G group chromosome, the 22 chromosome. The present work reports the chromosomal abnormalities observed in 39 patients with chronic myelocytic leukemia, studied at the Genetic Unit, in the Faculty of Medicine of Zulia University, during the period from 1987 to 1991. Sixty per cent of the patients showed different abnormalities, such as 8 trisomy, t (8;22), and in the remaining 15%, no chromosomal changes were detected. The patients with t (9;22) as the only abnormality, had less relapses and longer survival. The clinical course of 50% of the patients with normal karyotype was similar to those with t (9;22) as the only abnormality; the other 50% had an accelerated course with frequent relapses and early death. The present findings confirm that the presence of the Philadelphia chromosome as the only karyotypical abnormality, is indicative of better prognosis, and its association with other chromosomal changes predicts a more accelerated course that will probably require a more aggressive treatment.

Ectodermal dysplasia in females and inversion of chromosome 9.

Absence of sweat glands, hypotrichosis, hypodontia, characteristic facial features, and intolerance to heat, without dystrophia of the nails, are manifestations of sex linked hypohydrotic ectodermal dysplasia. Three males and two females were affected in a family in which the affected females were also carrying a pericentric inversion of chromosome 9. Those phenotypically normal females in this pedigree who were obligate carriers had normal karyotypes. One of the affected females (the proband) had, in addition, primary amenorrhoea, absence of the mammary glands, and rudimentary internal genitalia. The fact that clinical manifestations of ectodermal dysplasia in the carrier females of this family are only observed in those also carrying a pericentric inversion of chromosome 9 in peripheral blood leucocytes perhaps suggests that non-random inactivation of the paternal X chromosome has occurred as a consequence of the inversion.