Refining the genetic diagnostic puzzle: A case report on a Chinese ARPKD patient with a reciprocal balanced translocation and c.2507 T > C (p.V836A) in PKHD1.

INTRODUCTION: Autosomal recessive polycystic kidney disease (ARPKD) ranks among the most severe chronic kidney diseases (CKD). Its primary cause is variants in the Polycystic Kidney and Hepatic Disease 1 gene (PKHD1). The clinical spectrum of ARPKD varies widely, ranging from mild late-onset symptoms to severe perinatal mortality. However, achieving an early genetic diagnosis in ARPKD patients before clinical symptoms appear proves challenging.

CASE PRESENTATION: This case is a 4-year-old boy who experienced a convulsion characterized by a generalized tonic attack lasting approximately 3-5 minutes and later sought treatment to our hospital. However, routine abdominal ultrasound examination accidentally detected that he had diffuse liver lesions, splenomegaly, and bilateral renal enlargement with renal pelvis dilation. Given the uncertainty regarding the underlying cause of the patient's structural abnormalities and convulsions, karyotyping, whole exome sequencing (WES), structural variant analysis (SV analysis) of whole genome sequencing (WGS) were recommended. The result of SV analysis revealed that he has an RBT impacting PKHD1 and the precise location of breakpoints was confirmed through Long-Range Polymerase Chain Reaction (LR-PCR). However, WES did not screen out pathogenic variants initially, the WES data was reviewed subsequently based on SV analysis results.

CONCLUSION: We identified an infrequent variant combination, c.2507T>C (p.V836A) in PKHD1 and an RBT with broken PKHD1, which extends the genetic spectrum of ARPKD, and provide a basis for further genetic counselling to the family.