# Atypical Liver Ultrasound Image in a Boy with Autosomal Recessive Polycystic Kidney Disease (ARPKD) and New PKD1 Variant—A Case Report

## TL;DR

A 5-year-old boy with ARPKD showed unusual liver cysts and a new PKD1 mutation, highlighting genetic complexity in kidney and liver disease.

## Contribution

First reported case of large hepatic cysts in ARPKD with dual PKHD1-PKD1 variants and a novel PKD1 mutation.

## Key findings

- Patient had atypical liver ultrasound findings with large hepatic cysts not typical for ARPKD.
- Genetic analysis revealed dual PKHD1 variants and a new PKD1 mutation.
- PKD1 mutation may explain the unusual liver phenotype despite normal maternal imaging.

## Abstract

Background: Autosomal recessive polycystic kidney disease (ARPKD) is a rare form of PKD that leads to the development of multiple renal cysts and hepatic fibrosis. Aim: The first documented case of large hepatic cyst associated with dual PKHD1-PKD1 variants. Case report: We present the case of a 5-year-old boy with a kidney US image typical of ARPKD and numerous large cysts in the liver not typical for this disease. Genetic analysis revealed heterozygous missense mutations in the PKHD1 gene (maternally, c.107C>T/p.Thr36Met in exon 3; paternally, c.4870C>T/p.Arg1624Rrp in exon 32) and an additional new variant in PKD1 (maternally, c.5323G>A/p.Gly1775Ser in exon 32). Genetic tests excluded mutations in genes responsible for polycystic liver disease (PCLD). However, the presence of the PKD1 mutation is clinically not clear due to the normal abdominal US image in the mother; it seems to be the most likely explanation for unusual phenotype in our patient. Conclusions: This case may contribute to the understanding of the phenotypic variability in ARPKD and the potential modifying role of mutations in other PKD-related genes. Comprehensive genetic panels are crucial for explaining atypical phenotypes and prognosis in patients with PKD.