Triploid/diploid mosaicism (69XXY/46XX) presenting as severe early onset preeclampsia with a live birth: placental and cytogenetic features

Use of tissue samples in diagnosing diploid triploid mosaicism

Diploid triploid mosaicism (DTM) is a rare genetic condition where there is an extra haploid set of chromosomes in mosaic form. We describe an infant for whom DTM was detected antenatally through amniocentesis. Prenatal counselling suggested a guarded prognosis. The infant's phenotypic presentation and postnatal course reflect the varied presentation and prognosis associated with DTM. We highlight potential challenges in diagnosing DTM postnatally, with many having normal blood karyotype with 46 chromosomes.

Normal female phenotype and ovarian development despite the ovarian expression of the sex-determining region of Y chromosome (SRY) in a 46,XX/69,XXY diploid/triploid mosaic child conceived after in vitro fertilization-intracytoplasmic sperm injection

CONTEXT

Diploid/triploid mosaicism (mixoploidy) is a rare chromosomal abnormality characterized by mental and growth retardation, hypotonia, and dysmorphic features such as facial asymmetry, low-set ears, and syndactyly. All 46,XX/69,XXY cases fall into three phenotypic groups: male with testicular development, ovotestis disorder of sex development (DSD), or undervirilized male DSD. All phenotypic females with diploid/triploid mosaic reported so far had 46,XX/69,XXX karyotype.

PATIENT

We report an 8-year-old girl conceived after in vitro fertilization-intracytoplasmic sperm injection with normal internal/external genital and ovarian development despite 46,XX/69,XXY mosaicism and normal expression of sex-determining region of Y chromosome (SRY) in her gonads.

INTERVENTION

Because of the increased risk of gonadoblastoma resulting from Y chromosome mosaicism, her ovaries were removed by laparoscopy. Ovarian tissue was analyzed histologically as well as by fluorescence in situ hybridization, PCR, and RT-PCR amplification to determine the localization of Y chromosome and expression of SRY and DAX1 mRNA. Methylation-specific PCR was used to assess the inactivation pattern of X chromosomes.

RESULTS

By laparoscopy, internal female genital anatomy appeared to be normal. Cytogenetic and molecular methods confirmed the presence of intact and functionally active Y chromosome in the ovary. Strikingly, histological assessment of the gonads showed normal ovarian architecture with abundant primordial follicles despite the presence of the Y chromosome in ovarian follicles and the expression of SRY mRNA in gonadal tissue.

CONCLUSION

This case illustrates that normal ovarian development is possible in the presence of Y chromosome in ovarian follicles and despite the expression of SRY in ovarian tissue. Furthermore, this is the first documented case of mixoploidy after in vitro fertilization-intracytoplasmic sperm injection and the only phenotypic female with 46,XX/69,XXY karyotype.

Transient progeroid phenotype and lipodystrophy in mosaic polyploidy

Wiedemann-Rautenstrauch syndrome is a rare disorder with a progressive course and early lethality. Severe mental and growth retardation, muscle hypotonia, a progeroid face, wrinkled skin, relative macrocephaly with late closure of the anterior fontanel, arachnodactyly and congenital heart defects are also typical. We report on a female infant with all the characteristic features of this syndrome after birth. Chromosomal studies on peripheral leukocytes showed a normal karyotype. In view of an abnormal lipid distribution and lipodystrophy, metabolic studies for congenital disorders of glycosylation have been performed with normal results. At the age of 2 years 6 months the progeroid signs were no longer present, and the patient had a striking improvement in her psychomotor development. As there are overlapping features in Wiedemann-Rautenstrauch syndrome and in mosaic polyploidy, including psychomotor retardation, reduced peripheral muscle bulk, arachnodactyly and lipodystrophy, chromosome analysis was performed in the fibroblast culture of our patient. A mosaic triploidy/tetraploidy was detected in 60% and 14% of the cells, respectively. We therefore recommend chromosome analysis of fibroblasts from patients with a neonatal presentation of progeroid features and lipodystrophy.

The parent-of-origin effect of 10q22 in pre-eclamptic females coincides with two regions clustered for genes with down-regulated expression in androgenetic placentas

By affected sib-pair linkage analysis of 24 families with pre-eclampsia, we confirm a susceptibility locus on chromosome 10q22.1 in Dutch females: a multipoint non-parametric linkage score of 3.6 near marker D10S1432 was obtained. Haplotype analysis showed a parent-of-origin effect: maximal allele sharing in the affected sibs was found for maternally derived alleles in all families, but not for the paternally derived alleles. As matrilineal inheritance suggests the presence of maternally expressed imprinted genes, while imprinting operates predominantly in (extra)embryonic tissues, all genes (n=132) known on 10q22 between GATA121A08 and D10S580 were screened for seven sequence-related features associated with imprinting and subsequently tested for expression in first trimester placenta. Placental expression of genes selected in this way (n=55) was compared with expression in androgenetic placentas of identical gestational age. Two regions on 10q22 were identified with developmentally co-repressed genes with non-random chromosomal distribution. Interestingly, these two clusters, near CTNNA3 and KCNMA1 and each containing five genes with down-regulated expression in androgenetic placentas, coincided with the regions with maximal maternal allele sharing seen in the pre-eclamptic sisters. Our linkage and expression data are compatible with the concept that pre-eclampsia involves maternally expressed imprinted genes that operate in the first trimester placenta.