Genetic Investigation of Pregnancies With an Isolated Fetal Pelvic Kidney.

This retrospective study includes 212 fetuses with an isolated pelvic kidney found on second-trimester anatomy ultrasound, all tested by chromosomal microarray (CMA) and, optionally when CMA was negative, by trio exome sequencing. CMA identified a single pathogenic CNV, a de novo 16p11.2 microdeletion. Among 118 fetuses tested by trio exome, five disease-causing variants (4.2%) were found in five unrelated fetuses, in DLL1, KMT2D, PTEN and PRKG1, including two distinct KMT2D variants. After phenotype-genotype correlation, only the two KMT2D variants were deemed clinically attributable, giving an attributable yield of 1.7% (2/118), the other three being classed as incidental findings; all variants were de novo except the PRKG1 variant, inherited from the mother.

Synthesis written by Geno'X. For the full original abstract, please refer to the source publication.

The 1.7% attributable yield is low and does not by itself justify systematic exome sequencing for an isolated pelvic kidney, but the two KMT2D cases are a reminder that an apparently isolated renal anomaly can reveal a syndrome. The careful separation of attributable variants from incidental findings is a methodological strength in the prenatal setting, where the ultrasound phenotype is limited. Exome uptake in 118 of 212 cases leaves room for selection bias.

Analysis by Dr Thibaut Benquey