To address this question, we studied five newly identified MVID subjects in which we found homozygous STX3 variants; in addition, we investigated five previously described MVID subjects with STX3 variants (Alsaleem et al. 2017; Julia et al. 2019; Maddirevula et al. 2019; Wiegerinck et al. 2014) for the presence or absence of symptoms of marked visual impairment. This evidence concerns the gene STX3 and microvillus inclusion disease.