Very Rare Congenital Malformations: Responsibilities of Scientists

Abstract

somewhat obscure journal and in French, this case remained unnoticed to Englishspeaking scientists until 1995, when Spencer [3] described it in the English literature, resolving the myth about the existence of rachipagus conjoined twins. Asymmetrical parasitic rachipagus conjoined twins occur more often, but are however also rare. More than 20 cases have been found [4, 5] . Unfortunately, the only knowledge we have on the skeletal anatomy of symmetrical rachipagus conjoined twins was the radiograph published in the article by Betoulieres et al. [2] in 1960. Knowledge of the morbid anatomy of rachipagus conjoined twins remained very limited [4] , and several questions are still unanswered (e.g., how are the vertebral columns and skulls fused; which parts of the skulls and vertebrae are missing?). Nothing is known about the anatomy of the internal organs especially the central nervous system (e.g., are the brains and spinal cords fused?). More questions remained unanswered (e.g., why are rachipagus conjoined twins so extremely rare; why do parasitic rachipagus conjoined twins occur more often?). Some scholars doubt the existence of rachipagus conjoined twins and consider the case of Betoulieres et al. [2] as a fabrication. All we could do was to wait for another example to occur, which could be examined in more detail with modern technology. Multiplanar MR imaging techniques can provide anatomical In a recent issue of Fetal Diagnosis and Therapy , Durin et al. [1] reported on the fi rst trimester diagnosis and subsequent abortion of a pair of symmetrical rachipagus conjoined twins. The authors described the transvaginal ultrasound and provided brief details of the post-abortion examination of the conjoined twin pair: ‘Macroscopic analysis revealed female twins with separate faces. Eight members were individualized with malposition of the four feet. Autopsy revealed separate digestive and genitourinary tracts, but both fetuses showed right kidney agenesia. There were two anuses. Spinal cords were separated with fusion of posterior fossae. Vertebral bodies were fused. These observations were compatible with conjoined cranio-rachi-pygopagus.’ They illustrated their article with three fi gures: two images of the transvaginal ultrasonography at 12 weeks’ gestation and one image of the intact aborted conjoined twin pair. Their conclusion that this concerns an extremely rare type of conjoined twins is correct; in fact it is the second documented case of this congenital malformation. In 1960 Betoulieres et al. [2] published a similar case. This concerned newborn female symmetrical rachipagus conjoined twins which were united from the top of the crania to the buttocks. The vertebrae between T6 and L3 were fused with one spinal canal. Only one radiograph of the conjoined twins illustrated this case report. Published in a