Supplementary Material for: Coexistence of mosaic marker chromosome and isodisomy 1 in reproductive failure: A cytogenomic case report and review of the literature

IAbstract Introduction: Reproductive failure has been associated with various chromosomal abnormalities, including small supernumerary marker chromosomes (sSMCs). In rare cases, uniparental disomy (UPD) may also contribute to reproductive problems, particularly when invoving imprinted regions or in cases of isodisomy where autosomal recessive disorders may manifest. UPD involving chromosome 1 (UPD1) is rare and has not been linked to a consistent phenotype. Case Presentation: We present a 27-year-old woman with a five-year history of reproductive difficulty, including one biochemical pregnancy loss and one clinically recognized miscarriage at 8 weeks of gestation. Cytogenetic analysis revealed mosaicism for a small supernumerary marker chromosome derived from chromosome 1. SNP microarray identified complete UPD1 without copy number changes. Fluorescence in situ hybridization (FISH) confirmed centromeric material of chromosome 1 in the marker chromosome. Conclusion: To the best of our knowledge, this is the first reported case combining mosaic sSMC(1) and complete UPD1 in a phenotypically healthy woman with reproductive failure. The coexistence of these abnormalities likely reflects a postzygotic chromosomal rescue mechanism. These findings underscore the diagnostic value of integrated cytogenomic analyses in unexplained reproductive failure and subfertility. Keywords: reproductive failure, supernumerary marker chromosome, isodisomy, uniparental disomy, cytogenetics, case report