A parapagus dicephalus tripus tribrachius conjoined twin with a unique morphological pattern: a case report

Abstract

Background Conjoined twinning is a rare congenital malformation with an incidence of about 1.5 per 100,000 births. Because no consensus has been reached regarding the dysmorphology, thorough descriptions of conjoined twins as part of teratological collections can be useful to increase knowledge of this congenital malformation. In this case report, we describe a parapagus dicephalus twin from the collection of the Department of Anatomy of the University Medical Center Utrecht in the Netherlands. External anatomical characteristics were assessed through a detailed macroscopic examination and internal characteristics by means of whole-body computed tomography and magnetic resonance imaging (3 Tesla). Case presentation Macroscopic examination showed a Caucasian male parapagus dicephalus tripus tribrachius conjoined twin a type of conjoined twinning in which there are two heads side by side, one rump, and three upper and three lower limbs. In addition, anencephaly was observed in the left twin. Radiological imaging showed a normal central nervous system in the right twin and absence of the calvaria, cerebrum, diencephalon, and mesencephalon in the left twin. There was clear duplication of the vertebral column, rib cage, respiratory system, and gastrointestinal system at least up to and including the first part of the duodenum. The heart consisted of a monoatrium with two separate ventricles. There was a fused liver with a single gallbladder, a single spleen, three kidneys, two bladders, and duplication of the penis. The third upper and lower extremities were articulating with a fused glenoid and acetabulum, respectively. The third foot showed both polydactyly and syndactyly of the toes. Conclusion This case report describes a unique case of a male dicephalus parapagus tripus tribrachus conjoined twin discordant for anencephaly. Radiological imaging proved to be an adequate noninvasive method to provide insights into the internal (dys)morphology of this specific specimen, improving its scientific and educational value. This approach could be generally applied to other teratological specimens, thereby strengthening arguments regarding pathogenetic hypotheses, which may lead to new or improved insights into both normal and abnormal embryonic development.

Characterizing the coalescence area of conjoined twins to elucidate congenital disorders in singletons

“…Severe congenital anomalies (late) in the third trimester are nowadays rare in developed countries, where methods for prenatal assessment of the unborn child are ubiquitous. It is noteworthy that the (scientific) literature concerning conjoined twins often uses the wrong terminology and classification and that etiopathogenetic mechanisms are erroneously interpreted, incomplete, too vague, or just too brief to comprehend and are often incompatible with knowledge about normal embryological development (Bovendeert, Nievelstein, Bleys, & Cleypool, 2020 ; Spencer, 2003 ). Moreover, most case reports concern only external dysmorphological aspects.…”

Phenotypically Discordant Anomalies in Conjoined Twins: Quirks of Nature Governed by Molecular Pathways?

“…Laterally united conjoined twins share vast parts of their body (abdomen, thorax, neck, face and/or head) and classically consists of two phenotypes: parapagus dicephalus (two heads) and parapagus diprosopus (two laterally oriented faces in a single compound head). One of the more striking and relatively often occurring discordances found in dicephalic twins is anencephaly, with at least seven described cases appearing in the recent literature [9,14,15,[25][26][27][28]56]. These unilaterally occurring neural tube defects should be distinguished from concordant neural tube defects in parapagus diprosopus, which are the consequence of interaction aplasia, a phenomenon comprehensively described elsewhere [3].…”

“…Before one can start describing any concomitant anomaly in conjoined twins, one should be acquainted with the semantics that should be used for these dysmorphological patterns and should know how they ought to be interpreted, as observations and descriptions of concomitant anomalies are oftentimes misinterpreted [13] or rather superficially etiologized [14,15]. The first dichotomy is to divide anomalies by their topographical location.…”