How does terminal 21q22 deletion really manifest? Delineation based on prenatal diagnosis and literature review

Most genetic disorders, especially rare and manifested with an unspecific constellation of developmental anomalies, are challenging to diagnose before birth. The paper aims to present a rare case of terminal 21q22 deletion to extend the knowledge on this rare genetic disease, mostly to facilitate prenatal guidance by pointing the diagnostic features.

The fetus was diagnosed prenatally, at 21 weeks of gestation, due to ultrasound markers detected in a routine ultrasound scan. Post-mortem dysmorphological assessment has verified the diagnosis. To the best of our knowledge, this is the second report of prenatal presentation of partial monosomy 21q.

By giving the detailed phenotype description and presenting a comprehensive literature review on the subject, we delineate its phenotype, which was different from what has been shown in the literature. Specifically, the clinical presentation of aberration within regions 2 and 3 (referring to the term proposed by Lyle et al., in 2009) of 21q22 bands is not characterised by multiple or severe malformations, which matters for prenatal counselling and diagnostics.