Chromosomal mosaicism in amniotic fluid cell cultures

Abstract

Six cases of chromosomal mosaicism detected in amniotic fluid cultures are described. In five of these there was no evidence of fetal mosaicism. In one case fetal mosaicism was demonstrated but only by the study of fibroblasts since blood cultures showed only normal cells. The implications of amniotic fluid mosaicism are discussed and it is concluded that this usually does not indicate fetal mosaicism. The value of repeated amnio‐centesis in the diagnosis of fetal mosaicism was demonstrated by findings in three of the cases. It is recommended that amniotic fluid cultures be harvested in situ for chromosome studies and that cytogenetic results be expressed as number of colonies karyotyped rather than as number of cells analyzed.

Prenatal diagnosis of trisomy 20 mosaicism

“…Mosaicism is diagnosed in amniotic fluid cell cultures when an aneuploid cell line is discovered in a proportion of cells in at least two or more cultured flasks or colonies. Most of the reports of mosaicism in am- niotic fluid cell cultures involve chromosomes associated with specific syndromes (Bloom et al 1974, Sutherland et al 1975, Milunsky & Atkins 1976, Dill et al 1977, Hsu et al 1978. In several cases, the mosaicism was confirmed postnatally (Bloom et al 1974, Hsu et al 1976, Milunsky & Atkins 1976, Dill et al 1977, Kohn et al 1977.…”

“…menon (Kardon et a1 1972, Bloom et al 1974, Sutherland et al 1975, Milunsky & Atkins 1976, Rudd e t al. 1976, Hsu et al 1976, Dill e t al.…”

Amniotic fluid cell mosaicism for presumptive trisomy 20

“…Chromosomal mosaicism in amniotic fluid cell cultures appears to manifest itself in two major categories: (1) a single colony, or only single cells are found with an aberrant karyotype; and (2) multiple colonies, or a substantial number of cells are found, all with identical aberrant karyotypes. In the first instance, the aberrations usually are of an uncommon type, not generally known to bc associated with an established viable chromosomal imbalance syndrome in man, and healthy children are born (Cox et al 1974, Kohn et al 1975, Sutherland et al 1975, Schmid 1976). Among 3,268 colonies from 448 amniotic fluid cell cultures, we observed eight such events (only a single colony affected with an aberration, mostly pseudodiploidy).…”

“…Among 3,268 colonies from 448 amniotic fluid cell cultures, we observed eight such events (only a single colony affected with an aberration, mostly pseudodiploidy). In the second instance, potentially viable types of chromosomal imbalance seem to be represented, e.g., trisomy 13 (Bloom et al 1974, Dill et al 1977, Klinefelter syndrome (Milunsky 19761, XO/XY mosaicism (Hsu et al 1976) or a small metacentric marker chromosome (case 6 of Sutherland et al 1975), and the mosaicism is confirmed in the fetus or at birth. According to their cytogenetic presentation (multiple colonies affected), both of our cases clearly belong in category 2.…”

Prenatal diagnosis of 45,X/46,XY mosaicism with postnatal confirmation in a phenotypically normal male infant

“…cism has always been a diagnostic dilemma. More than 20 cases of chromosomal mosaicism in cultured amniotic fluid cells have been reported (Kohn & Robinson 1970, Kardon et al 1972, Bloom et al 1974, Cox et al 1974, Katayama et al 1974, Kohn et al 1975, Sutherland et al 1975, Hsu et al 1976, Laurence & Gregory 1976. All of these pregnancies resulted in either phenotypically normal liveborns or grossly normal abortuses.…”