Long-term follow-up and analysis of monozygotic twins concordant for 45,X/46,XY peripheral blood karyotype but discordant for phenotypic sex

Successful surgical sperm retrieval from a patient with 45,X/46,XY mosaicism followed by in vitro fertilization pregnancy: A case report

RATIONALE

Mixed gonadal dysgenesis is a rare disorder of sex development, and typically contains a mosaic 45,X/46,XY karyotype.

PATIENT CONCERNS

We reported here a case of a 42-year-old man with infertility for 6 years and inability to ejaculate during intercourse.

DIAGNOSIS

Physical examination confirmed that the external genitalia was male. The right testis of this patient was resected and the left testis had intrascrotal calcification. Hormone test showed that the level of follicle-stimulating hormone was 20.14 IU/L (normal range, 1.27-19.26 IU/L). No deletion or mutation was found on the sex-determining region Y. H&E staining revealed seminiferous tubule dysgenesis. The karyotyping in peripheral blood and testicular tissue was 45,X/46,XY and 45,X/47,XYY/46,XY, respectively. Based on these results, the patient was diagnosed with 45,X/46,XY or 45,X/47,XYY/46,XY mosaicism and gonadal dysgenesis.

INTERVENTIONS

In vitro fertilization and embryo transfer technology were used to help his wife to achieve pregnancy.

OUTCOMES

A normal baby boy was born at 36 weeks of gestation with a karyotype 46, XY.

LESSONS

We reported a rare case of a karyotype 45,X/46,XY in blood cells and 45,X/47, XYY/46,XY in testicular tissue. In vitro fertilization and embryo transfer technology can help to achieve pregnancy.

Gender-Discordant Monochorionic-Diamniotic Twins Both With 45,X/46,X, Idic(Y) Mosaicism and a Novel Deletion Within the TBC1D5 Gene

The occurrence of monochorionic diamniotic twins with sex discordance is a very rare phenomenon. We present a case of spontaneously conceived gender-discordant monochorionic diamniotic twins born to a 23-year-old female, both twins demonstrating similar blood karyotype 45,X/46,X, idic(Y) and a novel 99 kb mutation at 3p24.3 involving exons 15-16 of transcript NM_001134381.1 of the Tre-2/Bub2/Cdc16 Domain Family Member 5 (TBC1D5) gene. The male twin showed no anatomic abnormalities and pelvic ultrasound revealed descended gonads. The female twin had a horseshoe-shaped kidney, normal uterus, and intra-abdominal gonads. The blood karyotype and microarray studies revealed similar distribution of X and isodicentric Y chromosome along with a novel genetic mutation which has not been previously reported. Our case findings not only report Turner syndrome mosaicism with a novel genetic mutation but also stress the importance of clinical follow-up of twins in order to evaluate the functional abnormalities associated with isodicentric Y chromosomes including germ cell tumors.

Identical but not the same: the value of discordant monozygotic twins in genetic research

Monozygotic (MZ) twins show remarkable resemblance in many aspects of behavior, health, and disease. Until recently, MZ twins were usually called "genetically identical"; however, evidence for genetic and epigenetic differences within rare MZ twin pairs has accumulated. Here, we summarize the literature on MZ twins discordant for Mendelian inherited disorders and chromosomal abnormalities. A systematic literature search for English articles on discordant MZ twin pairs was performed in Web of Science and PubMed. A total number of 2,016 publications were retrieved and reviewed and 439 reports were retained. Discordant MZ twin pairs are informative in respect to variability of phenotypic expression, pathogenetic mechanisms, epigenetics, and post-zygotic mutagenesis and may serve as a model for research on genetic defects. The analysis of single discordant MZ twin pairs may represent an elegant approach to identify genes in inherited disorders.