A twin sibling with Prader-Willi syndrome caused by type 2 microdeletion following assisted reproductive technology: A case report.

Prader-Willi syndrome (PWS) is a neurobehavioral imprinting disorder, which arises due to an absence of paternally expressed genes within the 15q11.2-q13 region. This occurs via one of the three main genetic mechanisms, as follows: Deletion of the paternally inherited 15q11.2-q13 region, maternal uniparental disomy and imprinting defect. Recent studies have reported an association between imprinting disorders and assisted reproductive technologies (ART). The current study presents a 6-year-old female patient who is a dizygotic twin, in which one was born with de novo microdeletion at 15q11.2-q13.1 following in vitro fertilization. The patient had characteristic facial features including narrow bifrontal diameter, strabismus, downturned mouth, feeding problems and generalized hypotonia during infancy, developmental delay, mental retardation and rapid weight gain. Based upon phenotypic resemblance and the medical records, methylation-specific multiplex ligation-dependent probe amplification and array-based comparative genome hybridization analyses demonstrate type 2 microdeletion between breaking point 2 (BP2) and BP3, which occur from MKRN3 through HERC2 at 15q11.2-q13.1. To the best of our knowledge, the present study is the first to report a PWS case born following ART reported in South Korea. In addition to previous studies, the present study contributes to the consensus regarding genotype-phenotype comparisons in this respect.