biostudies-literatureKawamura RJSPS KAKENHI8https://www.ebi.ac.uk/biostudies/studies/S-EPMC12914905biostudies-literatureUnknown19(1)<h4>Background</h4>Intrachromosomal insertion is a rare form of structural chromosomal rearrangement that often cannot be accurately delineated by conventional G-banding, making it difficult to predict reproductive outcomes. In clinical practice, such insertions are often misinterpreted as inversions or remain undetected, leading to recurrent segmental imbalances in offspring. We aimed to characterize an unresolved structural rearrangement identified in a family and to clarify its reproductive implications through advanced cytogenetic and molecular analyses.<h4>Methods</h4>Cytogenetic and molecular studies were conducted in a family where the proband exhibited a 17.8 Mb duplication at 9q21.31-q22.33. Although G-banding suggested a parental structural abnormality, its configuration could noMolecular cytogeneticsIntrachromosomal insertion as a diagnostic challenge: a hidden structural rearrangement causing recurrent duplication and deletion.PMC12914905JP23K06619Sugihara EHara TShichiri YTsuboi AKawamura RNaru YMurase YKurahashi HSatano HSuzuki HfalseIntrachromosomal insertion as a diagnostic challenge: a hidden structural rearrangement causing recurrent duplication and deletion.<h4>Background</h4>Intrachromosomal insertion is a rare form of structural chromosomal rearrangement that often cannot be accurately delineated by conventional G-banding, making it difficult to predict reproductive outcomes. In clinical practice, such insertions are often misinterpreted as inversions or remain undetected, leading to recurrent segmental imbalances in offspring. We aimed to characterize an unresolved structural rearrangement identified in a family and to clarify its reproductive implications through advanced cytogenetic and molecular analyses.<h4>Methods</h4>Cytogenetic and molecular studies were conducted in a family where the proband exhibited a 17.8 Mb duplication at 9q21.31-q22.33. Although G-banding suggested a parental structural abnormality, its configuration could no2026-01-01T00:00:00Z2026 Jan2026-07-09T11:10:39.572Z2026-07-09T10:42:35.162ZS-EPMC129149054158218210.1186/s13039-026-00748-5