Prenatal diagnosis of pure partial monosomy 18p associated with holoprosencephaly and congenital heart defects

•We used CMA and FISH analyses to build a correlation between 18p11.32–11.31 monosomy and a series of anomalies.•Tetralogy of Fallot and holoprosencephaly are showed in 18p11.32–11.31 monosomy patient.•18p11.3 was also important for HPE pathogenesis besides 18p11.1 or 18p11.2.

We applied CMA to detect chromosomal variations during a prenatal diagnosis and detected a 4.5 Mb pure microdeletion at 18p11.3 that was not detected by conventional karyotyping. Fluorescent in situ hybridization (FISH) analysis was performed to confirm the deletion. Accurate breakpoints of the deletion in this patient were used to build correlations between monosomy 18p and the concomitant phenotypes, particularly holoprosencephaly (HPE), which is rarely reported in monosomy 18p11.3.