T Peters-Brown | PubMed Health

PubMed1998

Familial supernumerary marker chromosome evolution through three generations.

A mosaic chromosome complement, 46,XY/47,XY,+r(15), was detected at prenatal diagnosis. Family studies showed the mother and one of her two children to have a bisatellited supernumerary marker chromosome (SMC) in all lymphocytes examined. The maternal grandfather also showed a bisatellited SMC, but in only 2 per cent of his lymphocytes. NOR, DA/DAPI, and chromosome 15 centromere and short arm-specific probes confirmed the identify of the bisatellited SMC and of ring SMC as derived from chromosome 15. An apparently normal male was born at full term. At age 1 year, the baby continues to have normal growth and development. The bisatellited 15 likely originated by somatic mutation in the grandfather (2 per cent cells), was transmitted unchanged to the daughter and grandson (germline transmission, no mosaicism), and then evolved by excising the satellites and forming a ring SMC in the index case. Progressive changes in the frequency and subsequent changes in the structure of this SMC illustrate the unusual characteristics of chromosome 15.

Adult↗

PubMedDate not supplied

Discrepancies in cytogenetic findings in chorionic villi.

We present a database and a review of published literature on discrepancies in chorionic villus (CV) diagnostic findings. The review includes 457 cases of discrepancies between CV findings (direct, culture, or both) and the fetus. One hundred and one cases reported normal by CV direct harvest included 30 with abnormal or mosaic abnormal fetal karyotype (30% false negatives). The corresponding number of false negatives for CV culture was only 4 cases out of 133 (3%). Assuming no bias in reporting cases based on site of discrepancy (assumption may not hold), these data imply that the probability of false-negative findings is 10-fold higher by CV direct method compared to CV culture method. We also reviewed recent studies reporting on large series of CV diagnosis. This review revealed that the reported overall frequencies of discrepancies as a percentage of abnormal and mosaic abnormal CV results ranged from 11 to 63% (a mean of 37%). These data, together with recent reports of survival of embryos with reported abnormal karyotypes because of confined placental mosaicism (CPM), raise several questions pertaining to the predictive value of CV sampling and the origin of the discrepancies in the fetal-placental unit. Caution is recommended in counseling patients undergoing CV sampling to provide appropriate follow-up studies in cases of possible discrepancies.

Chorionic Villi Sampling↗