46,XY monozygotic twins with discordant sex phenotype.
OBJECTIVE
To analyze male and female sex differentiation in monozygotic twins.


METHODS
Retrospective study.


METHODS
Multiple academic centers.


METHODS
A pair of monozygotic twins.


METHODS
Skin and blood samples were obtained for DNA analysis and karyotyping.


METHODS
Mutation within the SRY gene was analyzed by the polymerase chain reaction-single-stranded conformation polymorphism test. Monozygosity was ascertained by short tandem repeat analysis. Karyotypes were studied in blood and skin fibroblasts.


RESULTS
SRY was present in both twins, but no mutations were detected in the SRY conserved motif. Monozygosity was confirmed by the use of short tandem repeat analysis in four loci: c-fms, thyroid peroxidase, von Willebrand factor, and tyrosine hydroxylase. The karyotype was 46,XY uniformly in both twins.


CONCLUSIONS
Monozygotic twins can develop discordant male and female phenotypes despite the presence of a common karyotype and despite the presence of intact testis-determining genes. In the present case, this could be due to mutation or to mosaicism involving occult 45,X cell lines in the dysgenetic gonads.
Somkuti
S G
SG
Department of Obstetrics and Gynecology, Abington Memorial Hospital, Abington, Pennsylvania, USA.
Wachtel
S S
SS
Schinfeld
J S
JS
Jackson
L
L
Tharapel
A T
AT
DiGeorge
A M
AM
D004268:DNA-Binding Proteins / Q000235:genetics; D004200:Diseases in Twins; D005260:Female; D006061:Gonadal Dysgenesis, 46,XY / Q000235:genetics*; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D008297:Male; D009687:Nuclear Proteins; D010641:Phenotype; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D051876:Sex-Determining Region Y Protein; D020080:Tandem Repeat Sequences; D014157:Transcription Factors; D014430:Twins, Monozygotic / Q000235:genetics*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors