Different Laterality in Hereditary Monozygotic Twins with Duane Retraction Syndrome Type I: A Case Report

Simultaneous contraction of the medial and lateral rectus muscles results in Duane Retraction Syndrome (DRS). The presence of a familial pattern in some cases suggests an autosomal dominant mode of transmission. Despite the variable presentation of this syndrome, its cause remains unclear. Describing the potential factors contributing to DRS in monozygotic twins may be effective in explaining its etiology.

We report a unique case of monoamniotic monozygotic twins case both 7-year-old Iranian girls with DRS type I, inherited from their 36-year-old father with DRS type III. There was no clinical manifestation of DRS in the 38-year-old Iranian mother. One twin exhibited bilateral DRS, whereas the other manifested DRS exclusively in the right eye. In contrast, their father had DRS limited to the left eye. The unique laterality discordance in monozygotic twins emphasizes the role of gene expression patterns in the variability of DRS. These findings highlight the complex nature of clinical expression of DRS. Furthermore, we recognize the need to consider additional factors, such as placental dynamics, the environment, epigenetic modifications, and vascular development, for a comprehensive understanding of this condition.

While genetic factors may play a fundamental role in understanding DRS in twins, it is important to consider the interaction of placental, environmental, epigenetic, and vascular developmental factors for a comprehensive approach.