Meier–Gorlin syndrome due to a recurrent <i>DONSON</i> variant in a Turkish family: first report of thumb aplasia and long-term growth data

This is the third report of <i>DONSON</i> c.631C>T p.(Arg211Cys) in Turkish patients. While the recurrence in the same population suggests a founder effect, haplotype-based analysis is required. Thumb aplasia expands the known phenotype of <i>DONSON</i>-related MGORS, and the observed moderate course of growth retardation offers prognostic value. These findings highlight the importance of including <i>DONSON</i> in MGORS gene panels, considering population-specific variants, and systematically documenting rare phenotypic features to improve diagnosis, follow-up, and genetic counseling.