Prenatally Detected Maternally Inherited Partial Duplication of 11p15.5 ICR1 Results in Phenotypes Overlapping Russell‐Silver Syndrome in Infancy

Differentially methylated regions (DMRs) in certain areas of the genome are subject to genomic imprinting. DMRs at chromosome 11p15.5 are associated with Beckwith-Wiedemann syndrome (BWS) and Russell-Silver Syndrome (RSS), two growth disorders with opposite phenotypes. We identified a maternally inherited duplication containing part of the 11p15 DMR in a non-anomalous fetus in first trimester using genome sequencing (GS). The ∼281kb duplication at 11p15.5 contains the entire imprinting control region 1 (ICR1) and the H19 gene but lacks the IGF2 gene and the imprinting control region 2 (ICR2). Methylation studies revealed hypomethylation of ICR1 in fetal cells as well as in the mother (leukocytes), who had a history of feeding difficulties in infancy and short stature. The duplication was inherited from the asymptomatic maternal grandmother of the fetus, who showed hypermethylation of ICR1 in leukocytes suggesting paternal inheritance. The fetus developed decelerating growth in late gestation and phenotypes overlapping those of RSS were noted in infancy. This study adds to the limited literature on partial duplications of the 11p15.5 region and their associated phenotypes, underscoring the efficacy of GS in cases involving DMRs associated with imprinting disorders.