A case of true hermaphroditism reveals an unusual mechanism of twinning

@article{Souter2006ACO,
  title={A case of true hermaphroditism reveals an unusual mechanism of twinning},
  author={Vivienne Souter and Melissa A Parisi and Dale R. Nyholt and Raj P. Kapur and Anjali K. Henders and Kent E. Opheim and Daniel F. Gunther and Michael E. Mitchell and Ian A. Glass and Grant W. Montgomery},
  journal={Human Genetics},
  year={2006},
  volume={121},
  pages={179-185}
}
Traditionally twins are classified as dizygous or fraternal and monozygous or identical (Hall Twinning, 362, 2003 and 735–743. [] Key Method The twins underwent initial investigation with 17-hydroxyprogesterone and testosterone levels, pelvic ultrasound and diagnostic laparoscopy. Cytogenetic analysis was performed on peripheral blood cells and skin fibroblasts. Histological examination and Fluorescence in situ hybridization studies on touch imprints were performed on gonadal biopsies.

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A parthenogenetic maternal and double paternal contribution to an ovotesticular disorder of sex development

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The patient was a single maternal and double paternal genetic, which was a type of a parthenogenetic division of a maternal haploid nucleus into two identical nuclei, followed by fertilization by two spermatozoa and fusion of the two zygotes into a single individual at the early embryonic stage.

Uniparental Disomy in Somatic Mosaicism 45,X/46,XY/46,XX Associated with Ambiguous Genitalia

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The findings suggest that the observed complex DSD phenotype is the result of somatic gonosomal mosaicism and UPD despite a normal blood karyotype, and the presence of UPD warrants adequate genetic counseling for the family and frequent, lifelong, preventive follow-up controls in the patient.

Chimerism resulting from parthenogenetic activation and dispermic fertilization

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The results indicate that the chimerism in the authors' patient is the result of dispermic fertilization of a parthenogenetically activated oocyte, highlighting the difficulties in predicting the clinical outcome in patients with genetic aberrations in mosaic or chimeric form.

A case of blood chimerism and twin-to-twin transfusion syndrome in monochorionic dizygotic twins

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A recently systematic review by Peters, et al. finds 31 cases of MCDZ since 2000 to nowadays.

Molecular Support for Heterogonesis Resulting in Sesquizygotic Twinning.

TLDR
A monochorionic twin pregnancy with fetal sex discordance is reported, and detailed genotyping implicates chimerism arising at the juncture of zygotic division, termed heterogonesis, as the likely initial step in the causation of sesquizygosis.

Microchimerism in twins

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The most common gonad in patients with true hermaphroditism, an ovotestis, was found in 44.4% of 568 gonads, and Histologically the testicular tissue was described to be immature and only twice was spermatogenesis reported while the ovarian portion often appeared normal.

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This case of chimerism represents a true hermaphroditism that most probably developed by double fertilization of one or more egg nuclei by two sperms, with two alleles inherited from the father and one from the mother.

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The data suggest that the patient's hermaphroditism was the result of a mosaic embryo and not a chimera, resulting in the loss of 47,XXY cells during early embryonic development.

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TLDR
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TLDR
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