Craniofacial microsomia in a parasite of a heteropagus conjoined twin: A clinical and histopathologic evaluation

Abstract

This report evaluates a rare case of craniofacial microsomia in a partially developed, malformed heteropagus conjoined twin. In this instance, several major components of the craniofacial complex were involved: bones, cartilage, teeth, salivary glands, auditory apparatus, cerebrum, cranial nerves, and ocular neuroepithelium. In addition, cervical vertebrae and appendicular long bones were markedly affected. To date, the underlying disorder (whether genetic, metabolic, or environmental) responsible for the development of this congenital malformation is not fully understood. Our clinical and pathologic examinations tend to suggest that an apparent lack of an adequate arterial blood supply to the growing embryo could have contributed to the elaboration of this complex syndrome. The fact that the parasite's blood supply relied mainly upon a single, medium-sized artery (1.5 mm in diameter) could have brought about local ischemic milieus during the critical phases of embryogenesis; hence, impeding the preprogrammed migration of neural crest cells to their end targets in the upper branchial arches. In such a case, the normal sequence of cell differentiation is damaged, which in turn imposes a severe impact on the morphogenesis of the various tissues composing the craniofacial complex.

Recurrent constellations of embryonic malformations re‐conceptualized as an overlapping group of disorders with shared pathogenesis

“…LBWC, POC, and OEIS, all of which involve closure of either the neural tube or ventral body wall, likely are due to perturbations in very early pregnancy, whereas conditions such as MURCS, likely occur later in gestation. The one individual with OAVS that overlaps with OEIS had omphalocele, a defect that generally occurs later in the first trimester compared to ventral body wall closure, which may account for the OEIS/OAVS RCEM overlap (Silbermann, Bar‐Maor, & Auslander, 1984). Omphalocele can occur anytime between 6 to 10 weeks' gestation.…”

Heteropagus (parasitic) twins: a review

“…Selective ischemic atrophy of the deprived portion of the parasite's body follows. This theory has appeared in various iterations since that time [23,25,34,48,49]. In support of this speculation, autositederived vascular pedicles-apparently sustaining parasite tissues-are frequently identified during surgical separation and hypoplastic umbilical cords have been identified in parasitic twins with markedly absent caudal structures [47,50].…”