Parental mosaicism rather than de novo variants in FOXG1‐related syndrome and TUBA1A‐associated Tubulinopathy: Familial case reports

BackgroundDe novo variations are a primary cause of Rett syndrome and Tubulinopathy, accounting for over 90% of cases. Some studies have identified and documented parental inheritance by mosaicism in these two disorders, albeit with limited data.MethodsClinical characteristics and diagnosis, including genetic tests of members of two families, were obtained from medical reports.ResultsThe first family with Rett syndrome (RTT) presented with two offspring carrying FOXG1 c.460dup. Both affected RTT pregnancies did not show anomalies within the first trimester, preventing prenatal recognition at an early stage. The second family had two of three offspring confirmed with TUBA1A c.172G>A related to Tubulinopathy. Both young couples from the two families harbored none of the variants correlating to their children's conditions. Diagnosis of parental mosaics with higher rates of recurrence was reasonably determined, and genetic counseling played a major role in guiding and managing their subsequent pregnancies.ConclusionIn genetic disorders with a high penetration of de novo variants, the risk of having a recurrent baby is an important topic to discuss with affected families. By examining variants that siblings share, clinical diagnosis can offer valuable information about the presence of mosaic inheritance. To effectively manage in the long term, adequate genetic counseling and strategic planning for future pregnancies should be emphasized to mitigate the risk of recurrent offspring.