Familial Monozygotic Twinning: Report of an Extended Multi-generation Family

Hamamy, Hanan; Ajlouni, Heitham K.; Ajlouni, Kamel

doi:10.1375/136905204774200479

Cited by 32 publications

(12 citation statements)

References 15 publications

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“…In reality, there are two factors that negate this view. First, MZ twinning can be familial [Harvey et al, 1977;Shapiro et al, 1978;Hamamy et al, 2004;Machin, 2009]. Inheritance appears autosomal dominant in many cases.…”

Section: Mz Twinning Is Not a Random Teratogenic Eventmentioning

confidence: 99%

Non‐identical monozygotic twins, intermediate twin types, zygosity testing, and the non‐random nature of monozygotic twinning: A review

Machin

2009

American J of Med Genetics Pt C

137

102

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Monozygotic twins (MZ) are rarely absolutely “identical.” This review discusses the types of genetic/epigenetic and prenatal environmental post‐zygotic mechanisms that cause discordance within such twin pairs. Some of these mechanisms—ranging from heterokaryotypia to skewed X‐chromosome inactivation—may cause extreme discordance, but these extremes are merely the more emphatic examples of discordance that, to some degree, underlies the majority of MZ twin pairs. Because of the entrenched misconception that MZ twins are necessarily identical, many MZ twin pairs are mistakenly designated as dizygotic (DZ). Clinical benefits to accurate zygosity determination include correct solid organ transplantation matching, if one twin requires donation for a non‐genetically mediated disease; the opportunity of preventive management for disorders that do not manifest synchronously; and better counseling to parents regarding their individually unique, and often psychologically puzzling, twin offspring. In twin pairs with complex and confusing biological origins, more detailed zygosity testing may be required. For example, intermediate trigametic and tetragametic chimeric dizygotic twins are reviewed, some of whom are, nevertheless, monochorionic (MC). Because of inter‐fetal vascular anastomoses in MC twins, genetic results from blood samples may not accurately reflect discordance in solid organs. Previously, it was thought that MZ twinning was some sort of embryological fluke. However, familial monozygotic twinning is more common than suggested by the literature. Seven new families are presented in an accompanying paper. Despite the difficulties and dangers of twin pregnancy (especially so for MC twins), human twinning persists, and continues to both challenge and fascinate parents, clinicians and geneticists. © 2009 Wiley‐Liss, Inc.

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Section: Mz Twinning Is Not a Random Teratogenic Eventmentioning

confidence: 99%

Non‐identical monozygotic twins, intermediate twin types, zygosity testing, and the non‐random nature of monozygotic twinning: A review

Machin

2009

American J of Med Genetics Pt C

137

102

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“…While the genetic contribution to DZ twinning is well established, genetic associations with the occurrence of MZ twins have been described infrequently, and penetrance for this trait seems to be extremely low (Parisi et al 1983, Steinman 2003, Hamamy et al 2004. Monozygotic twin occurrence is universally about 0.4-0.45% following non-stimulated in vivo conception (MacGillivray 1986, Derom et al 1987.…”

Section: Introductionmentioning

confidence: 99%

Monozygotic twinning associated with assisted reproductive technologies: a review

Aston¹,

Peterson²,

Carrell³

2008

Reproduction

200

160

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Twin birth rates have increased markedly in developed countries since the 1970s for two primary reasons: increasing maternal age and the advent and increasing use of fertility treatments. In addition, monozygotic (MZ) twin pregnancies have been reported to occur at a significantly higher rate following assisted reproductive technologies (ART) procedures compared with the natural incidence. Twin pregnancies are of concern due to a dramatically increased risk of associated complications. Monozygotic twin pregnancies carry a 10-20% risk of twin-twin transfusion syndrome, and monoamniotic monochorionic twins are additionally at risk for cord entanglement. While the mechanisms and contributory factors for dizygotic twinning are well established, very little is known about the mechanisms involved in MZ twinning or the factors that contribute to its occurrence. In this review, we will discuss a number of potential mechanisms involved in MZ twinning and explore factors that may be contributing to the increased incidence of ART-associated MZ twins. An improved understanding of the factors that contribute to increased MZ twinning associated with ART will help to elucidate the poorly understood mechanisms involved in the process and will further aid in reducing the overall incidence of multiple pregnancies with their associated risks following ART procedures.

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“…6.8% cases had history of twin pregnancy in self or family members (Table 3). Hamamy et al (2004) 8 from their study of an extended multi-generation family reported familial monozygotic twinning compatible with autosomal dominant inheritance with reduced penetrance.…”

Section: Discussionmentioning

confidence: 99%