Twin zygosity testing for medical purposes

Successful Renal Transplantation between Identical Twins with Very Brief Immunosuppression

Renal transplantation between monozygous identical twins provides an opportunity to utilize minimal immunosuppression to maintain stable allograft function, thereby alleviating the toxicities of immunosuppressive therapy. Despite monozygosity, there is a possibility of discordant protein presentation in identical twins that could trigger alloimmune response and lead to graft injury. Therefore, the optimal immunosuppression regimen in this patient population is unknown, and the safety of immunosuppression withdrawal remains controversial. Herein, we describe two patients who underwent successful renal transplantation from monozygotic identical twin donors. Monozygosity was determined using short tandem repeat (STR) analysis. All immunosuppression was successfully discontinued at 2 days and 3 weeks, respectively, after transplantation. Both patients are alive with functioning renal grafts at 1 year and 5 years after transplant, respectively. These two cases suggest that immunosuppression can be withdrawn safely and rapidly in select monozygous identical twin renal transplant recipients.

Kidney transplant from a living monozygotic twin donor with no maintenance immunosuppression

From a theoretical point of view, an alloimmune response can not take place, still some type of standard immunosuppression is used in about 60% of patients receiving kidney grafts from their monozygotic twins. We aimed at assessing clinical response in patients receiving renal grafts from a living monozygotic twin donor when no immunosuppressive therapy is used.

METHODS

This is a retrospective observational study of patients receiving kidney grafts from their monozygotic twins from 1969 to 2013. The following data were recorded: age, renal graft recipient's primary disease, renal function, renal survival and overall survival. Immunosuppressive therapy included a single intraoperative dose of methylprednisolone 500 mg and no maintenance immunosuppression.

RESULTS

Five patients with kidney grafts from their monozygotic twins were dentified in our centre. Mean age at transplantation was 33 years (27-39). One-year overall survival and graft survival were 100%. Mean creatinine level was 0.96 ± 0.2 one year after transplantation, and 1.2 ± 0.37 mg/dl at most recent follow-up. Two patients died with a functional graft more than 15 years after kidney transplantation (causes were melanoma and cardiovascular event respectively). Follow-up was lost in a patient one year after transplantation. Two patients are alive with a functioning graft at 18 months and 42.5 years after transplantation respectively.

CONCLUSION

Kidney transplantation from a living monozygotic twin is associated to outstanding clinical outcomes. Immunossuppresive therapy to suppress alloimmune response in probably unnecessary 11 zygosity has been confirmed.

A lesson from kidney transplantation among identical twins: Case report and literature review

There continues to be disagreement related to the appropriate therapeutic regimen to be used when the donor and the recipient in kidney transplant operations are identical twins. Here we present two cases of kidney transplantation between identical twins. Both recipients had end-stage renal disease (ESRD) caused by primary nephropathy. We also present information gleaned from a literature review of similar cases. The first recipient was a 26-year-old man who experienced biopsy-proven IgA nephropathy 10 months post-transplantation. Mycophenolate mofetil (MMF), angiotensin receptor blockers (ARBs), and steroids were used to reverse this pathologic condition. Till now, 76 months post-transplantation, the patient is stable, and the new kidney is functioning well. The second recipient was a 20-year-old woman who had hematuria and proteinuria 3 months post-transplantation, and crescent glomerulonephritis with mild to moderate interstitial injury was proven by biopsy 11 months postoperatively. This patient did not respond to various treatments and resumed hemodialysis 15 months post-transplantation. These case studies show that immunosuppressive therapy should be maintained in kidney transplant recipients who are identical twins with ESRD caused by initial nephropathy.

Twins, Chorionicity and Zygosity

Accurate determination of zygosity and chorionicity is essential in all multiple maternities. The parents and the multiples themselves ask it. It is of medical importance and now considered as a prerequisite in several domains of twin research, especially when perinatal data are analysed. It helps the multiples and their parents and teachers to ascertain identity. The methods are briefly described and a plea is made to obstetricians and paediatricians to use them systematically at the time of birth.

Placentation in Multiple Births

Outcomes of multifetal pregnancy in prenatal life are markedly affected by chorionicity. Several disease processes are found in monochorionic (MC) twins that do not occur in dichorionic (DC) twins. Improvements in prenatal outcomes will depend on reliable first trimester diagnosis of chorionicity, allowing early monitoring for complications of MC placentation. Particular structures and functions of MC twin placentas affect outcomes and can be targeted for specific treatments, especially in twin-twin transfusion. The causes of severe DC twin fetal growth discordance are clarified. In post-natal life, zygosity is a determining effect in genetic predisposition to many chronic diseases, including neoplasia. Few MC twins know that they are monozygotic (MZ). Few twin researchers realize that MZ twins may be genetically discordant. Abandonment of the word “identical” for MZ twins would assist in clarifying these issues of zygosity, concordance and discordance.

Paternally Derived Twinning: A Two Century Examination of Records of One Scottish Name

Paternal influence on twinning was investigated through a study of all the state and church records of Scotland for the period 1800–2000 (nine generations) in relation to one Scottish patronymic — in total 50,000 births. All recorded twins born with the chosen patronymic were identified and their whole paternal ascent and descent on the male line were charted for twins. There were established three pedigrees A, B and C manifesting clear paternal twinning hereditary transmission. Detailed familial reproduction patterns were traced for pedigree A, including phenotypic identification of twin zygosity in relation to seven same sexed pairs of twins in the pedigree and one same sexed pair out of dizygotic triplets. It is the most comprehensive description to date of such a kind of twin familial trait. The data presented show (i) the unique feature of clear direct paternal influence on twinning in three families; (ii) paternal factor(s) determination in both DZ and MZ twinning; and (iii) a definite association of twinning tendency with a partial male infertility, which corresponds to the prediction of the Infertility/Twinning Paternally Dependent syndrome hypothesis. The hypothesis of a founder effect explaining the similarity of A, B, C families and the possible localisation of the paternally dependent twinning factor on the Y-chromosome are currently under molecular investigation.

Paternal Familial Twinning: Hypothesis and Genetic/Medical Implications

The phenomenon of paternally dependent familial twinning has been known in human and animal genetics since the 1920s, but still remains without any theoretical explanation and is indeed a neglected field of inquiry. Over the last two decades investigations in reproduction biology have discovered the significant role of multiple paternally dependent errors in fertilization including androgenic triploidy and moles. We suggest the hypothesis that the fathers of twins in the relevant families carry gene variants that increase the probability of dispermy, diplospermy and male pronucleus heterochrony as well as involvement of two male pronuclei in the fertilization of two female meiotic products. Any resulting twins would be an exceptional intermediate between MZ and DZ twins — and might properly be described as “sesquizygotic” (SZ). Paternal familial twinning may also go together with infertility due to triploidy, moles and chimerism. The hypothesis: (i) places the curiosities of paternally derived twinning within the framework of current knowledge of reproductive genetics and verifiable phenomena; (ii) predicts the existence of families in which twinning is associated with reproductive abnormalities; (iii) predicts an occurrence in relevant families of the third and intermediate category of SZ twins. Families with paternal twinning may thus provide the natural selective system for the search of unusual cases of primary chimeras, the frequency of which is still unknown.

The Frequency and Clinical Significance of Twin Gestations According to Zygosity and Chorionicity

Background:Although the clinical importance of chorionicity in twin pregnancies has been studied widely, the significance of perinatal determination of zygosity using molecular genetic analyses remains controversial. The purpose of this study was to determine the frequency and clinical significance of twin gestations according to zygosity and chorionicity in a Korean population.Methods:We enrolled 569 women who delivered twin newborns (> 24 weeks) at Seoul National University Hospital between 1999 and 2008. Chorionicity was established by histologic examination of placentae. Zygosity was determined with sex of neonates, chorionicity, and DNA analysis of umbilical cord blood.Results:The frequency of dizygotic (DZ) twins was 71.0% (404/569 pairs) based on the opposite sex (238/404 [58.9%]) and DNA analyses (166/404 [41.1%]); that of monozygotic (MZ) twins was 29.0% (165/569), including monochorionic (MC) (72.1% [119/165]) and dichorionic (DC) twins (27.9% [46/165]), which was confirmed by DNA analyses. Among spontaneously conceived twins, the frequency of MZ twins was more than twice that of DZ twins. The risk of low birth weight was 1.8-fold higher among MZDC twins and 1.9-fold higher among MZMC twins than among DZDC twins (p< .05). Bronchopulmonary dysplasia occurred more frequently among MZMC twins than among DZDC twins (adjusted OR 8.42, 95% CI 1.82–39.08,p< .01). However, the frequencies of other neonatal morbidities were not significantly higher in the MZMC group than in the MZDC and DZDC groups. The perinatal mortality rate was 15 per 1000 total births in the DZDC twins, 20 per 1000 total births in the MZDC and 56 per 1000 total births in the MZMC (p< .01).Conclusions:Although monozygosity was shown to be a risk factor for perinatal death and accurate determination of zygosity plays a great role in the future consideration of organ transplantation and twin studies, the value of zygosity determination along with chorionicity in relation to overall neonatal morbidity was not definite.

Renal transplantation in identical twins in United States and United Kingdom

BACKGROUND

The primary aim was to review the graft and patient survival of all recipients of a living identical twin donor renal transplant in the United States and United Kingdom, between 1988 and 2004. The secondary aim was to assess their maintenance immunosuppression.

METHODS

Data of all the patients who underwent living identical twin donor renal transplantation in the United States and United Kingdom during 1988-2004 were retrieved from United Network for Organ Sharing and UK transplant, respectively. Further data were retrieved by sending letters to the individual transplant units in the United Kingdom.

RESULTS

There were 120 living identical twin donor renal transplants in the United States and 12 in the United Kingdom during the study period. Graft survival was 99.17%, 91.84%, and 88.96% in the US group at 1, 3, and 5 years, respectively, and 83.3%, 83.3%, and 75% in the UK group during the same follow-up period. Patient survival was 100%, 97.01%, and 97.01% in the US group at 1, 3, and 5 years, respectively, and 100% in the UK group during the same 5-year follow-up period. A large number of patients were on some form of immunosuppression.

CONCLUSIONS

Graft and patient survival were good in both countries. These results are better than those published in the literature over the previous 20 years. Although phenotypic differences in monozygotic twins can exist, immunosuppression may be unnecessary in all these patients. Ideally, all identical twins who are currently on immunosuppression should undergo zygosity testing to establish whether they should continue the immunosuppression unless they need it for another reason.

Monozygotic transplantation: concerns and opportunities

We describe the case of a 24-year-old female with end-stage renal disease from focal segmental glomerulosclerosis (FSGS) diagnosed at age 16, who underwent monozygotic triplet transplantation at age 21 from her sister. Monozygosity was established by buccal smear DNA PCR amplification using short tandem repeat (1) profiling for 16 genetic alleles. All immunosuppression was discontinued by 1 month posttransplant. To evaluate the use of immunosuppression in HLA identical monozygotic transplantation, we interrogated the OPTN (Organ Procurement Transplant Network) database for all transplants conducted from 1987 to 2006. We identified 194 probable identical twin transplantations based on age, gender, race, ethnic category, blood type and HLA match. We evaluated the use of various immunosuppressive agents at discharge, 6 months and 1, 2 and 3 years after transplantation. Seventy-one percent of these patients at discharge and 34% at the end of 1 year were on immunosuppression. At discharge 61% received steroids and 30% received calcineurin inhibitors and 66% of these remained on calcineurin inhibitors at 1 year. Renal function was superior among those not maintained on immunosuppression. Thus, monozygotic transplantation confers an immunologic advantage that allows immunosuppression elimination despite a risk of recurrent glomerular disease such as FSGS with appropriate evaluation and management.

Transplantation in identical twins: another option for breast reconstruction

BACKGROUND

Deriving their name from the Greek word plastikos, meaning related to molding, plastic surgeons have made their reputation by transplanting tissues from one area of the body to another to "remold" defects caused by trauma, congenital anomaly, or disease. Dr. Joseph Murray, a plastic surgeon, performed the first successful kidney transplant between identical twins in 1954. The authors present three cases involving the transplantation of perforator flaps from one identical twin to another for breast reconstruction, including cases using both deep inferior epigastric perforator and superficial inferior epigastric artery flaps.

METHODS

Three sets of recipient monozygotic twins that had breasts treated with mastectomies underwent reconstruction using transplanted tissue from their donor monozygotic twins. All sets of twins underwent DNA testing to determine that they were monozygotic; therefore, no immunosuppressive therapy was indicated.

RESULTS

The three sets of recipient monozygotic twins underwent successful breast reconstruction using perforator flap transplants from their donor monozygotic twins. The operations included two unilateral reconstructions (one using a deep inferior epigastric perforator flap and the other using a superficial inferior epigastric artery flap) and one bilateral deep inferior epigastric perforator reconstruction. Their hospital courses were unremarkable.

CONCLUSIONS

Transplant surgery continues to evolve in the twenty-first century. The authors present three cases of breast reconstruction using skin flap transplantation as a new option for breast reconstruction.

Living donor transplantation between twins: guidance for Donor Advocate Teams

Using a clinical case, this paper explores the ethical complexities of assessing potential living organ donors when the proposed donor-recipient pair consists of monozygotic (identical) or dizygotic (fraternal) twins. While all donor-recipient pairs can present various ethical and psychosocial challenges, the challenges of twin pairs are unique and especially complex. Donor Advocate Teams need to be aware of these unique issues and address them during their assessment process.

Determination of twin zygosity using a commercially available STR analysis of 15 unlinked loci and the gender-determining marker amelogenin – a preliminary report

BACKGROUND

The aim of this preliminary study was to estimate the accuracy of the zygosity determination in twin pregnancies.

METHODS

Seventy-three sets of twin pregnancies were enrolled in this study, including 48 sets of twins resulting from assisted reproductive techniques (ART) and 25 sets of spontaneously conceived twins. Determination of zygosity was made by PCR-amplified short tandem repeat (STR) analysis with a commercially available panel, comprising 15 autosomal, codominant, unlinked loci and the gender-determining marker, amelogenin. Monozygotic (MZ) twins were determined when all these unlinked loci and the gender-determining marker were identical. Chorionicity and placenta were examined after delivery of the newborns to check their relationships to the twin zygosities.

RESULTS

Three of 48 (6.25%) sets of twins produced by ART and 18 of 25 (72%) sets of spontaneously conceived twins were MZ. Monozygosity could be evaluated based on 'like sex' in spontaneously conceived twins, because they had a greater incidence of MZs than those produced by artificial reproductive techniques. The MZ prediction rate was 78.6%, and the overestimated rate was 21.4% if the monochorionic like-sexed twins (LST) had a grossly single placenta. The underestimated rate of MZs was 26.7% when the dichorionic LST had apparently separate placentas.

CONCLUSION

With the DNA-based 15 STR analysis amplified in a multiplex PCR, the determination of the zygosity in multifetal pregnancies is not only cost and time saving but also yields greater sensitivity and precision than conventional methods.

Epidemiology and biology of multiple gestations

Twins have always aroused interest and have been represented throughout history. Conjoined twins have caused even more sensation, the best-known pair being Chang and Eng Bunker, who were born in Thailand in 1811 and inspired the term Siamese twins. Recently, higher-order multiples have caused controversy, and there has been heavy media coverage of large-number deliveries, such as the McCaughey septuplets. In this article, we review the incidence, types, and causes of multiple gestations.

Prenatal diagnosis of zygosity by fetal DNA analysis, a contribution to the management of multiple pregnancies. A series of 31 cases

OBJECTIVE

To evaluate the contribution of prenatal diagnosis of zygosity by fetal DNA analysis to the management of multiple pregnancies.

METHODS

Between March 1999 and March 2000, 31 same-sex multiple pregnancies, were referred to our Institute during their second trimester to have amniocentesis done. Fetal DNA variants were studied in addition to karyotype. The main indications for amniocentesis were fetal growth discordance, fetal malformations or selective pregnancy termination. Zygosity results were compared to the first-trimester ultrasound diagnosis.

RESULTS

21 out of the 31 multiple pregnancies were dizygous, and 10 out of the 31 pregnancies were monozygous. First-trimester ultrasound provided information on chorionicity only in 24 out of the 31 cases (77%). Of these 24 reports, 21 proved to be correct (87.5%). Moreover, in 2 cases among 14 pregnancies with growth discordance, DNA analysis ruled out a twin-to-twin transfusion syndrome, while ultrasound could not yield a conclusion. In 2 twin pregnancies with fetal malformations affecting one of the fetuses, DNA analysis made it possible to assess the risk for the other twin. In the 5 cases leading to selective termination, prenatal diagnosis of zygosity had a decisive value for the surviving fetus.

CONCLUSION

Fetal DNA analysis is a simple and highly useful test for prenatal diagnosis of zygosity in the management of complicated multiple pregnancies.

Mechanisms for differences in monozygous twins

Monozygous (MZ) twins are often described as being physically and genetically identical. Clinical determination of zygosity relies on the assumption that any physical differences between a pair of twins imply they are dizygous. Most twin research relies on the assumption that dizygous twins share approximately 50% of the same genes, whereas monozygous twins share 100%. There is, however, increasing evidence to challenge both these assumptions. In this review, we describe a number of intrauterine effects and genetic mechanisms that may result in phenotypic, genotypic, and epigenetic differences between monozygous twins. Newer molecular techniques are resulting in such differences being increasingly commonly recognised. The potential for differences in monozygotic twin pairs is an important consideration for both clinicians and researchers involved in twin work.