Prenatal Diagnosis of Renal Cysts and Diabetes Syndrome (RCAD): A Case Report.

BACKGROUND Renal cysts and diabetes syndrome (RCAD), caused by heterozygous variants or whole-gene deletions in the HNF1B gene, is a rare, multisystem disorder often detected prenatally by ultrasound findings of bilateral cystic or hyperechogenic kidneys. CASE REPORT We present the case of a 21-year-old woman (G3P2) at 19 weeks of gestation referred for detailed fetal evaluation due to bilateral hyperechogenic, polycystic kidneys and severe oligohydramnios. After counselling, an amnioinfusion was performed to enable amniocentesis and cytogenetic testing. Chromosomal microarray analysis identified a 1.4 Mb interstitial deletion at 17q12 (arr 17q12(34,850,785_36,248,926)x1), encompassing the HNF1B gene and consistent with RCAD syndrome. Family history revealed maternal renal cysts and paternal early-onset diabetes. Despite conservative management and monitoring, the pregnancy was complicated by intrauterine infection, leading to fetal death. CONCLUSIONS This case report expands the spectrum of prenatal findings associated with RCAD and emphasizes the importance of integrating ultrasonographic, genetic, and familial data in the diagnostic pathway. Chromosomal microarray analysis remains a pivotal tool for prenatal detection of HNF1B deletions and for differentiating RCAD from other cystic kidney diseases, such as autosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD), which require targeted gene sequencing. Recognition of RCAD in the prenatal setting enables precise counselling, recurrence risk assessment, and postnatal follow-up planning for affected families.