Mosaic trisomy 1q: a recurring chromosome anomaly that is a diagnostic challenge and is associated with a Fryns-like phenotype.

OBJECTIVE

Trisomy of the long arm of chromosome 1 is a very rare cytogenetic anomaly that is difficult to diagnose because of tissue-limited mosaicism. This study aimed to further characterize the prenatal and post-natal findings associated with this anomaly, including the first reported chromosomal microarray finding.

METHOD: This is a retrospective study of six cases of mos 46,X,der(Y)t(Y;1)(q12;q21)/46,XY, diagnosed both prenatally and post-natally. Detailed clinical features and pregnancy outcome were documented.

RESULTS

Recurrent prenatal and post-natal features of our case series, as well as the previously reported cases, were described, suggesting a Fryns-like phenotype. A diagnosis of mosaic trisomy 1q is difficult to confirm post-natally in some cases because of the tissue provided for analysis, emphasizing the need to study multiple tissue types in cases of fetal loss with a suspected underlying chromosomal imbalance.

CONCLUSION

The overlap of clinical features between mosaic trisomy 1q and Fryns syndrome emphasizes the need to obtain appropriate samples for genetic analysis. The present cases and a review of the literature suggest that partial trisomy of the long arm of chromosome 1 is a distinct de novo clinical entity with low recurrence risk. © 2017 John Wiley & Sons, Ltd.