Autosomal Recessive Polycystic Kidney Disease Confirmed to PKHD1 Gene Mutation: A Case of PKHD1 Gene Mutation

Autosomal recessive polycystic kidney disease (ARPKD) is a severe form of polycystic kidney disease that is characterized by enlarged kidneys and congenital hepatic fibrosis. The clinical spectrum of this condition shows wide variation. Approximately 30-50% of affected individuals die in the neonatal period, while others survive into adulthood. ARPKD is caused by mutations in the polycystic kidney and hepatic disease 1 (PKHD1) gene on chromosome 6p12, which consists of 86 exons variably assembled into many alternatively spliced transcripts. We report a case of a pathogenic PKHD1 frameshift mutation, c.889_931del43, which was identified using direct full sequencing, associated with enlarged cystic kidneys and dilatation of intrahepatic bile duct, as observed on imaging studies.

Molecular Characteristics and Functions of PKHD1 / 生物化学与生物物理进展

PKHD1 ( polycystic kidney and hepatic disease 1), the causal gene of human autosomal recessive polycystic kidney disease(ARPKD), is located on chromosome 6p12.2 and covers a genomic region of ～500 kb. PKHD1 is among the largest human genes, with a minimum of 86 exons from which multiple transcripts may be generated by alternative splicing. The longest continuous open reading frame consists of 12 222 bp, encoding a 4 074 amino acid protein, designated as fibrocystin/polyductin (FPC). FPC is predicted to be a receptor like protein, with single transmembrane domain and a short cytoplasmic tail. The expression of mouse FPC can be detected in various duct-containing organs. In mouse embryogenesis, FPC appears in developing neural tube, bronchi, and the primordial gut as early as the day of E9.5. In fetal human kidneys, high level of FPC expression is present in ureteric bud and its expression continues throughout the process of renal tubuobranching. In adult human kidneys, FPC mainly expresses in the epithelia of renal collecting ducts. FPC is subcellularly localized to the primary cilia and concentrated on the basal bodies in renal epithelial cells. The detail function of FPC is still unrevealed, most recent studies demonstrate that FPC, as a receptor, may transduce cell signal by interacting with a trp superfamily TRPP2 (PKD2), which is a causal gene for ADPKD, and mediate intracellular calcium homeostasis to regulate differentiation, proliferation, migration and polarity of various duct/tubular epithelia, in turn, to modulate the formation of all physiologic ducts, tubules and tracts.

Longterm Follow-up of Autosomal Recessive Polycystic Kidney Disease

PURPOSE: This study was aimed to assess the clinical manifestations and courses of autosomal recessive polycystic kidney disease (ARPKD). METHODS: The medical records of 10 children diagnosed as infantile or juvenile ARPKD at Seoul National University Children's Hospital between January, 1984 and December, 1996, were reviewed, retrospectively. RESULTS: The average age at diagnosis was 3 8/12 years (4months-7 3/12 years) and sex ratio was 1 : 1. The mean follow-up duration was 8 5/12 years. Family history of renal cystic disease or hepatic fibrosis was not detected in any cases. Bilateral enlarged kidneys were noted in 2 cases and hepatosplenomegaly in all cases. Renal function had been maintained normally in all cases during follow-up. Urinary abnormalities were revealed in 4 cases and hypertension in 2 cases. Although liver enzyme levels were normal in all cases, esophageal varix was detected in 6 cases by gastrofiberscopy, and two of them received Warren shunt operation. The shunt operation did not affect the progression of the renal lesion. In 2 patients, who were diagnosed initially as congenital hepatic fibrosis, the renal cystic changes of ARPKD were detected 3 years and 6 years later. CONCLUSION: Because of the heterogeneous clinical spectrum and variable rate of progression of renal and hepatic lesion in ARPKD, the detection rate may vary. So patients, suspected to have ARPKD or congenital hepatic fibrosis, should be regularly followed up to detect latent renal lesion through radiological or pathological studies.