Turner syndrome with rare karyotypes

Boczkowsk, Krzysztof; Mikkelsen, Margareta; Poulsen, Hanne

doi:10.1111/j.1399-0004.1978.tb04139.x

Cited by 11 publications

References 7 publications

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Mental retardation and Ullrich‐Turner syndrome in cases with 45,X/46,X,+ mar: Additional support for the loss of the X‐inactivation center hypothesis

et al. 1994

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Four cases having mosaicism for a small marker or ring [45,X/46,X,+mar or 45,X/46,X,+r] chromosome were ascertained following cytogenetic studies requested because of minor anomalies (cases 1, 3, and 4) and/or short stature (cases 2 and 4). While all 4 cases had traits typical of Ullrich-Turner syndrome (UTS), cases 1, 3, and 4 had manifestations not usually present in UTS, including unusual facial appearance, mental retardation/developmental delay (MR/DD) (cases 3 and 4), and syndactylies (case 1). The facial appearances of cases 1 and 3 were similar yet distinct from that of case 4. Using fluorescence in situ hybridization (FISH), each of the markers in these 4 cases was identified as having been derived from an X chromosome. The level of mosaicism for the mar/r(X) cell line in these cases varied from 70% (case 1) to 16% (case 4) but was not apparently correlated with the presence of MR/DD. Replication studies demonstrated a probable early replication pattern for the mar/r(X) in cases 1, 3, and 4, while the marker in case 2 was apparently late replicating. To date, 41 individuals having mosaicism for a small mar/r(X) chromosome have been described. Interestingly, most of the 14 individuals having a presumedly active mar/r(X) demonstrated clinical findings atypical of UTS, including abnormal facial changes (11) and MR/DD (13). MR was noted most frequently in those cases having at least 50% mosaicism for the marker or ring. In contrast, atypical UTS facial appearance or MR/DD was not noted in 14 of the 16 cases with UTS who carried a probable late replicating marker or ring. In conclusion, although the phenotype of 45,X/46,X,mar/r(X) individuals appears to be influenced by the genetic content and degree of mosaicism for the mar/r(X), the most significant factor associated with MR/DD appears to be the activity status of the mar/r(X) chromosome. Thus, our 4 cases provide further support for the hypothesis that a lack of inactivation of a small mar/r(X) chromosome may be a factor leading to the MR and other phenotypic abnormalities seen in this subset of individuals having atypical UTS.

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Mental retardation and Ullrich‐Turner syndrome in cases with 45,X/46,X,+ mar: Additional support for the loss of the X‐inactivation center hypothesis

et al. 1994

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Phenotypic-Karyotypic Correlations of Gonadal Determinants: Current Status and Relationship to Molecular Studies

Simpson¹

1987

Human Genetics

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The similarity of phenotypic effects caused by Xp and Xq deletions in the human female: a hypothesis

Therman

Susman

1990

Hum Genet

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We have collected from the literature adult nonmosaic women with the following aberrant X chromosomes: Xp- (52), Xq- (67), idic(Xp-)(10), idic(Xq-)(9), and interstitial deletions (12). Lack of Xp, and especially Xcen-Xp11 (b region), may cause full-blown Turner syndrome. However, individual Turner symptoms, including gonadal dysgenesis, otherwise seem to be randomly distributed with respect to the different Xp and Xq deletions, although breakpoints distal to Xq25 do not give rise to any phenotypic anomalies except in a few cases of secondary amenorrhea or premature menopause. Of the carriers of an Xp- or Xq- chromosome, 65% and 93%, respectively, suffer from ovarian dysgenesis, whereas all idic(Xp-) and idic(Xq-) chromosomes cause primary or secondary amenorrhea. Xq deletions do not induce specific symptoms different from those caused by Xp deletions. Lack of the tip of Xp has led in 46/52 cases to short stature, but 43% of the Xq- carriers are also short. To explain these observations, we propose the following hypothesis. Since deletions of truly inactivated regions do not seem to cause any symptoms, we assume that the b region (Xcen-p11) always stays active in a normal inactive X, but is inactivated in deleted X chromosomes, especially in Xq- chromosomes. In some cases, inactivation may spread to the tip of Xp; this would explain the apparently variable behavior of the Xg and STS genes, and the short stature of some Xq- carriers. Full chromosome pairing seems to be a prerequisite for the viability of oocytes and thus for gonadal development. Deleted X chromosomes necessarily leave a portion of the normal X unpaired and isodicentrics probably interfere with pairing, resulting in atresia of oocytes. The role played by the "critical region" (Xq13-q24) in ovarian development is still unclear.

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Turner syndrome with rare karyotypes

Cited by 11 publications

References 7 publications

Mental retardation and Ullrich‐Turner syndrome in cases with 45,X/46,X,+ mar: Additional support for the loss of the X‐inactivation center hypothesis

Mental retardation and Ullrich‐Turner syndrome in cases with 45,X/46,X,+ mar: Additional support for the loss of the X‐inactivation center hypothesis

Phenotypic-Karyotypic Correlations of Gonadal Determinants: Current Status and Relationship to Molecular Studies

The similarity of phenotypic effects caused by Xp and Xq deletions in the human female: a hypothesis

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