Polycystic kidney disease

Whole exome sequencing approach for identification of the molecular etiology in pediatric patients with hematuria

BACKGROUND

Hematuria is a common condition in clinical practice of pediatric patients. It is related to a wide spectrum of disorders and has high heterogeneity both clinically and genetically, which contributes to challenges of diagnosis and lead many pediatric patients with hematuria not to receive accurate diagnosis and early management.

METHODS

In this single center study, 42 children with hematuria were included in Tianjin Children's Hospital between 2019 and 2020. We analyzed the clinical information and performed WES (Whole exome sequencing) for all cases. Then the classification of identified variants was performed according to the American College of Medical Genetics and Genomics (ACMG) guidelines for interpreting sequence variants. For the fragment deletion, qPCR was performed to validate and confirm the inherited pattern.

RESULTS

For the 42 patients, 16 cases had gross hematuria and 26 had microscopic hematuria. Molecular genetic causes were uncovered in 9 (21.4%) children, including 7 with Alport syndrome (AS), one with polycystic nephropathy and one with lipoprotein glomerulopathy. The genetic causes for other patients were not related with hematuria.

CONCLUSIONS

WES is a rapid and effective way to evaluate patients with hematuria. The analysis of genotype-phenotype correlations of patients with AS indicated that severe variants were associated with early kidney failure. Secondary findings were not rare in Chinese children, thus the clinician should pay more attention to the clinical interpretation of sequencing results and properly interaction with patients and their family.

Inhibition of Pkhd1 impairs tubulomorphogenesis of cultured IMCD cells

Fibrocystin/polyductin (FPC), the gene product of PKHD1, is responsible for autosomal recessive polycystic kidney disease (ARPKD). This disease is characterized by symmetrically large kidneys with ectasia of collecting ducts. In the kidney, FPC predominantly localizes to the apical domain of tubule cells, where it associates with the basal bodies/primary cilia; however, the functional role of this protein is still unknown. In this study, we established stable IMCD (mouse inner medullary collecting duct) cell lines, in which FPC was silenced by short hairpin RNA inhibition (shRNA). We showed that inhibition of FPC disrupted tubulomorphogenesis of IMCD cells grown in three-dimensional cultures. Pkhd1-silenced cells developed abnormalities in cell-cell contact, actin cytoskeleton organization, cell-ECM interactions, cell proliferation, and apoptosis, which may be mediated by dysregulation of extracellular-regulated kinase (ERK) and focal adhesion kinase (FAK) signaling. These alterations in cell function in vitro may explain the characteristics of ARPKD phenotypes in vivo.

PKHD1 protein encoded by the gene for autosomal recessive polycystic kidney disease associates with basal bodies and primary cilia in renal epithelial cells

Mutations of the polycystic kidney and hepatic disease 1 (PKHD1) gene have been shown to cause autosomal recessive polycystic kidney disease (ARPKD), but the cellular functions of the gene product (PKHD1) remain uncharacterized. To illuminate its properties, the spatial and temporal expression patterns of PKHD1 were determined in mouse, rat, and human tissues by using polyclonal Abs and mAbs recognizing various specific regions of the gene product. During embryogenesis, PKHD1 is widely expressed in epithelial derivatives, including neural tubules, gut, pulmonary bronchi, and hepatic cells. In the kidneys of the pck rats, the rat model of which is genetically homologous to human ARPKD, the level of PKHD1 was significantly reduced but not completely absent. In cultured renal cells, the PKHD1 gene product colocalized with polycystin-2, the gene product of autosomal dominant polycystic disease type 2, at the basal bodies of primary cilia. Immunoreactive PKHD1 localized predominantly at the apical domain of polarized epithelial cells, suggesting it may be involved in the tubulogenesis and/or maintenance of duct-lumen architecture. Reduced PKHD1 levels in pck rat kidneys and its colocalization with polycystins may underlie the pathogenic basis for cystogenesis in polycystic kidney diseases.

A novel gene encoding a TIG multiple domain protein is a positional candidate for autosomal recessive polycystic kidney disease

Autosomal recessive polycystic kidney disease (ARPKD) is a common hereditary renal cystic disease in infants and children. By genetic linkage analyses, the gene responsible for this disease, termed polycystic kidney and hepatic disease 1 (PKHD1), was mapped on human chromosome 6p21.1-p12, and has been further localized to a 1-cM genetic interval flanked by the D6S1714/D6S243 (telomeric) and D6S1024 (centromeric) markers. We recently identified a novel gene in this genetic interval from kidney cDNA, using cloning strategies. The gene PKHD1 (PKHD1-tentative) encodes a novel 3396-amino-acid protein with no apparent homology with any known proteins. We named its gene product "tigmin" because it contains multiple TIG domains, which usually are seen in proteins containing immunoglobulin-like folds. PKHD1 encodes an 11.6-kb transcript and is composed of 61 exons spanning an approximately 365-kb genomic region on chromosome 6p12-p11.2 adjacent to the marker D6S1714. Northern blot analyses demonstrated that the gene has discrete bands with one peak signal at approximately 11 kb, indicating that PKHD1 is likely to have multiple alternative transcripts. PKHD1 is highly expressed in adult and infant kidneys and weakly expressed in liver in northern blot analysis. This expression pattern parallels the tissue involvement observed in ARPKD. In situ hybridization analysis further revealed that the expression of PKHD1 in the kidney is mainly localized to the epithelial cells of the collecting duct, the specific tubular segment involved in cyst formation in ARPKD. These features of PKHD1 make it a strong positional candidate gene for ARPKD.

Sonographic pattern of recessive polycystic kidney disease in young adults. Differences from the dominant form

BACKGROUND

To study the sonographic pattern of autosomal recessive polycystic kidney disease (ARPKD) in early adulthood in order to identify imaging criteria to diagnose this disease and to distinguish between recessive and autosomal dominant polycystic kidney disease (ADPKD) in that age group.

METHODS

An abdominal ultrasound was performed on four ARPKD subjects (with a mean age of 20.2) and on 33 ADPKD subjects in early adulthood (29 without renal failure with a mean age of 20.5, and four with renal failure with a mean age of 26.5). Linkage studies with ADPKD and ARPKD markers were compatible with the clinical diagnosis in all cases.

RESULTS

The renal sonographic features in ARPKD subjects included multiple small cysts in a normal-sized kidney, increased cortical echogenicity and loss of corticomedullary differentiation. In ADPKD subjects without renal failure, sonographic features included few or multiple cysts of different sizes, in normal-sized kidneys in 22 out of 29 patients (75.8%), normal cortical echogenicity and conserved corticomedullary differentiation, except in patients with nephromegaly. All ADPKD subjects with renal failure had nephromegaly and loss of corticomedullary differentiation. The hepatic sonographic features in ARPKD patients included portal fibrosis and in some cases Caroli's disease, while in ADPKD patients a normal hepatic echostructure was detected in all but one case, in addition to simple hepatic cysts in a few cases.

CONCLUSIONS

The evaluation of the sonographic features of the kidneys and those of the liver may help in the differential diagnosis between ARPKD and ADPKD in early adulthood.

Abdominal sonographic study of autosomal dominant polycystic kidney disease

PURPOSE

The purpose of this study was to determine whether kidney size in patients who have autosomal dominant polycystic kidney disease (ADPKD) is related to renal function, hypertension, or extrarenal manifestations of the disease and to sonographically evaluate the abdominal manifestations of ADPKD.

METHODS

Between 1994 and 1998, 400 individuals from 85 families with a history of ADPKD were examined. There were 213 persons with ADPKD and 187 unaffected family members; there were 182 males and 218 females, 1-82 years old (mean, 39.3 years). We obtained a complete medical history, performed a physical examination, measured the arterial blood pressure and serum creatinine levels, and performed abdominal sonography on each subject. The sonographic features that were studied were renal length and the presence and number of cysts on the kidneys, liver, and pancreas.

RESULTS

There was a relationship between kidney size and age (p < 0.05), kidney size and renal function (p < 0.001), and kidney size and hypertension (p < 0.001). The overall prevalence of hepatic cysts in patients with ADPKD was 67%, and the prevalence increased with age. The presence of hepatic cysts was related to the severity of renal disease. Females had more severe polycystic liver disease, and massive polycystic liver disease (ie, hepatomegaly with innumerable cysts) was seen only in females. The prevalence of pancreatic cysts in the 187 persons in whom the pancreas was well evaluated sonographically was 5%.

CONCLUSIONS

Kidney size in patients with ADPKD is related to renal function, hypertension, and extrarenal involvement and can be used to predict the outcome of the disease. Hepatic cysts are very common in patients with ADPKD and are related to age and renal function; pancreatic cysts are infrequent in these patients.

Autosomal recessive polycystic kidney disease: radiologic-pathologic correlation

Autosomal recessive polycystic kidney disease is a heritable but phenotypically variable disorder characterized by varying degrees of nonobstructive renal collecting duct ectasia, hepatic biliary duct ectasia and malformation, and fibrosis of both liver and kidneys. In the kidney, the dilated collecting ducts and interstitial fibrosis, when severe, may significantly impair renal function and result in hypertension and renal failure. Imaging typically shows large but reniform kidneys, diffusely increased renal parenchymal echogenicity at ultrasonography, and a striated nephrogram after contrast material administration. In the liver, periportal fibrosis accompanies the malformed and dilated bile ducts; this may result in portal hypertension. The liver may appear normal or may show intrahepatic biliary dilatation; once portal hypertension develops, splenomegaly and varices are usually evident. The relative degrees of kidney and liver involvement tend to be inverse: Children with severe renal disease usually have milder hepatic disease, and those with severe hepatic disease tend to evidence mild renal impairment. Presently, treatment consists of supportive management and control of hypertension. Replacement therapy for renal failure (dialysis or kidney transplantation) and control of portal hypertension (portal circulatory diversion or liver transplantation) may be necessary.

Diagnosis of fetal renal anomalies

Urinary tract abnormalities are fairly common in the perinatal period. Ultrasonography is an effective diagnostic tool for identifying fetal urinary tract anomalies and can be helpful in establishing prognosis and guiding treatment decisions. The sonographer is encouraged to characterize and localize the fetal urinary tract abnormality when identified. In doing so, the correct diagnosis can be selected from the differential possibilities, providing vital clinical information needed to develop a care plan for both the pregnant woman and her fetus.

Autosomal recessive polycystic kidney disease

Autosomal recessive polycystic kidney disease is a rare inherited disorder which usually becomes clinically manifest in early childhood, whereas autosomal dominant polycystic kidney disease usually is a disorder of adult onset. With increasing knowledge and improving diagnostic techniques, it becomes evident that the spectrum of both entities is much more variable than generally known. The presentation of autosomal recessive polycystic kidney disease at later ages and survival into adulthood have been reported. The diagnostic criteria, clinical course, genetics and differential diagnosis of autosomal recessive polycystic kidney disease will be presented.

A tale of two prior probabilities--avoiding the false positive antenatal diagnosis of autosomal recessive polycystic kidney disease

We describe a case in which the typical ultrasound diagnosis of infantile polycystic kidney in a woman with no family history of renal disease was not confirmed by histology following termination of the pregnancy. This is contrasted with the situation in another couple who were known carriers of autosomal recessive polycystic kidney disease and where the prenatal ultrasound diagnosis was confirmed histologically. When prior genetic risk is low, the possibility of a normal or less severe outcome must be discussed with parents when fetal ultrasound shows large, echogenic kidneys but normal amniotic fluid volume.

The mouse polycystic kidney disease mutation (cpk) is located on proximal chromosome 12

The mouse congenital polycystic kidney (cpk) mutation produces a condition that resembles human autosomal recessive polycystic kidney disease (ARPKD) in its pattern of inheritance, clinical progression, and histopathology. Inheritance of this mouse mutation in crosses segregating the Rb(12.14)8Rma translocation chromosome and various DNA markers of Chromosome 12 have localized cpk to a site near D12Nyu2, approximately 7 cM from the centromere of Chromosome 12. This result suggests that the homologous PKD2 gene should be localized to either human chromosome 2p23-p25 or chromosome 7q22-q31.

Unilateral abdominal mass: an unusual presentation of autosomal dominant polycystic kidney disease in children

Autosomal dominant polycystic kidney disease is rarely diagnosed in infancy or childhood. The renal involvement is typically bilateral. We describe two children with ADPKD (autosomal dominant polycystic kidney disease) presenting with a unilateral renal mass. The value of a careful genetic history and the role of sonography will be discussed.

Adult polycystic disease of kidneys: a potential cause of false-positive 67Ga images

A 56-year-old man with adult polycystic disease of the kidneys complicated by renal failure, hypertension, and bacteremia underwent bilateral nephrectomy because the enlarged kidneys compromised his gastrointestinal function and respiratory capacity. A scan using 99mTc-methylene diphosphonate demonstrated nonfunctioning kidneys, bilaterally. An unusual radioactivity pattern in the bowel in 67Ga scintigraphy was due to extreme renal enlargement and should be kept in mind to avoid misinterpretation.

Adult polycystic kidney disease: a review of 100 cases

Herein we review 100 cases of adult polycystic kidney disease. Flank pain was the most common presentation in these cases. In 20% of the patients calculi were noted and 10% had obstruction. The average patient age at death was 57 years. The importance of tomography is emphasized with key radiographic features, such as bilateral large kidneys, inhomogeneous nephrogram, caliceal distortion and poorly defined renal margins. Cystic involvement of the liver and spleen may help to confirm the diagnosis. Differential diagnosis includes bilateral multiple simple cysts, angiomyolipomatosis and bilateral renal carcinomas.