A Case of Bilateral Microphthalmia and Extensive Colobomas of the Globes Associated with a Likely Pathogenic Homozygous SIX6 Variant

Colobomas of the globe and microphthalmia are congenital conditions that can strongly affect vision. Etiologies are varied and include embryonic and hereditary origins. We report what is, to the best of our knowledge, the first case of a SIX6 gene pathogenic variant associated with a phenotype of both bilateral microphthalmia and extensive colobomas of the globes. A 3-week-old boy presented with bilateral microphthalmia and iris, optic nerve, and chorioretinal colobomas. Genetic analysis was performed on a panel of 78 genes (microphthalmia, anophthalmia, and coloboma panel), and a homozygous likely pathogenic variant was identified in the SIX6 gene, resulting in the loss of the initiator methionine. Thus, our report expands the phenotypic spectrum of SIX6-related disorders.