Craniofacial Abnormalities in Twins at Tygerberg Hospital, Craniofacial Unit

Abstract

There is no article in the literature correlating only craniofacial abnormalities in twins. Since 1985 the Tygerberg Craniofacial Unit has treated nine pairs of twins. In this retrospective study, the authors correlate the craniofacial and systemic anomalies with the specific twin type. The frequency of human twinning varies from 1 in 30 to 1 in 150 pregnancies. These can be monozygotic (MZ) or dizygotic (DZ). Monozygotic or identical twins occur when a single ovum is fertilized, so the twins possess an identical set of nuclear genes. DZ twins result from the fertilization of two separate ova. Of the nine sets of twins, six were MZ (identical) and three DZ. Twelve patients presented with craniofacial abnormalities (CFA), which ranged from deformational plagiocephaly, scaphocephaly, trigonocephaly, to frontonasal dysplasia. Craniosynostosis was the most common CFA. Associated abnormalities included facial, limb, and cardiac defects. Twins with CFA are rare. The authors found that MZ twins are affected more and are more likely to have both siblings affected. DZ twins are affected less and are unlikely to have a co-twin affected.