Dysmorphism in one of a set of male twins; Could they have been identical twins? A diagnostic dilemma

Abstract

Twinning occurs worldwide, but Nigerian women of the southwest extraction record one of the highest rates in the world. Among the notable risk factors for fraternal twinning is advanced maternal age, which is also an independent risk factor for Down syndrome. Even as morphological characteristics can easily be applied to distinguish identical from fraternal twins, in cases of an associated dysmorphism, in any member of the couplet, it becomes a difficult tool to use, as has been observed in the case of a set of twins who were of the same sex, blood group, hemoglobin genotype, and shared the same placenta.

Suspected Down Syndrome in one of non-identical twins in Ile-Ife: A case report

“…From the discordant sex and dichorionic diamniotic placentation, the twins were dizygotic. The incidence of dizygotic twinning shows regional variations, with the Yorubas of southwest Nigeria having the highest global incidence, as high as 49 per 1000 live births [1,2]. Kuti et al reported an incidence of 42.59/1000 deliveries in Ile-Ife, Osun state [5], where our patient hailed from.…”

“…Non-identical twins with Down syndrome occur at the rate of 14-15 per million [2,6], demonstrating its rarity, and hence this report. The occurrence of Down syndrome in one twin of a dizygotic pair is plausibly explained by the fact that in dizygotic twins, each twin has an independent risk for Down syndrome with Apgar scores of 7 and 10 at one and five minutes respectively, while twin 2 was female, weighed 2.59 kg, with Apgar scores of 9 and 10 at one and five minutes respectively.…”

“…The mechanisms involved in multiple pregnancies equally predispose to various forms of congenital anomaly [2], including trisomy 21 (Down syndrome). The risk of Down syndrome is also independently heightened by increasing maternal age.…”

“…In the NICU, Twin 1 was observed to rarely cry, sleeping for most of the time. Owing to financial constraint, patient could not do karyotyping to confirm the clinical suspicion of Down syndrome in Twin 1 [2]. In about 95% of cases, Down syndrome is due to meiotic nondisjunction resulting in an extra copy of chromosome 21 (trisomy 21), the majority of cases occurring during maternal oogenesis [4,7].…”

“…With the increasing practice of assisted reproduction and as more women delay childbearing for various reasons (including career) worldwide, twinning incidence is rising globally [1,2]. The risk of Down syndrome increases with maternal age but occurs rarely in twins [3,4].…”