45,X/46,XY mosaicism: report of 27 cases.
OBJECTIVE
There exist substantial differences between prenatally and postnatally diagnosed cases of 45,X/46,XY mosaicism. Ninety percent of prenatally diagnosed cases show a normal male phenotype, whereas the postnatally diagnosed cases show a wide spectrum of phenotypes. This 10% risk of an abnormal outcome in prenatally diagnosed cases requires further attention. The purpose of the present study is to provide more information on the postnatally diagnosed 45,X/46,XY mosaicism cases. To date, only a few series have been reported. An accurate diagnosis in these patients is essential not only to their follow-up, but also to providing appropriate genetic counselling and subsequent prenatal diagnosis to their parents.


METHODS
The clinical, cytogenetic, endocrinologic, histologic and molecular biological findings of 27 patients with 45, X/46,XY mosaicism are analyzed.


RESULTS
The reported cases showed a wide spectrum of phenotypes as Turner syndrome, mixed gonadal dysgenesis (MGD), male pseudohermaphroditism (MPH) and apparently normal male. However, Ulrich-Turner stigmata were the most common features found in this series. Patients with MGD or MPH presented with various degrees of sex reversal such as hypospadias and/or abnormal internal genitalia. No correlation between the proportion of the 45,X/46,XY cell lines in the blood or the fibroblasts and the phenotype was found. Mild mental retardation was present in 4 of the patients and 2 patients showed signs of autism.


CONCLUSIONS
Two major points are emphasized in this series: 1) the presence in 7 histologically analyzed streak gonads of a homogeneous 45,X chromosomal complement suggests that the invasion of the primitive genital ridge by a such a cell line may induce abnormal gonadal development; 2) 3 males, apparently normal at birth, developed late onset abnormalities such as dysgenetic testes leading to infertility, Ulrich-Turner stigmata, dysmorphic features, and mild mental retardation. These data indicate the importance of an accurate clinical and histologic evaluation of any patient presenting with 45, X/46,XY mosaicism.
Telvi
L
L
Laboratoire de Cytogénétique, Hôpital Saint Vencent de Paul, 82, avenue Denfert Rochereau, 75674 Paris Cedex 14, France. telvi.l@filnet.fr
Lebbar
A
A
Del Pino
O
O
Barbet
J P
JP
Chaussain
J L
JL
D012734:Disorders of Sex Development / Q000235:genetics*; D006060:Gonadal Dysgenesis, Mixed / Q000235:genetics*; D006801:Humans; D007621:Karyotyping; D008297:Male; D009030:Mosaicism; D010641:Phenotype; D012729:Sex Chromosome Aberrations; D014424:Turner Syndrome / Q000235:genetics*; D014998:Y Chromosome