P696: Genome sequencing diagnoses atypical 7q11.23 region deletion in an adult patient

of absence of heterozygosity (AOH) on chromosome 13.These results were collectively interpreted as mosaic T13 following trisomy rescue with largely unpredictable outcomes.To further investigate the true level of the mechanism, a long-term culture (14 days) was analyzed by a second microarray to be contrasted to the direct array data.This analysis demonstrated a more pronounced T13 signal, now exceeding the reporting threshold, with the two AOH regions retained, indicating a higher true mosaicism level in the fetal tissue (23% vs previous 8%).These findings highlight that long-term amniocyte culture provides a more accurate assessment of tissue mosaicism, and that co-occurrence of trisomy and AOH on the same chromosome reflect a trisomy rescue mechanism.However, clinical outcomes remain unpredictable and depend on multiple factors.