PKHD1 mutations in families requesting prenatal diagnosis for autosomal recessive polycystic kidney disease (ARPKD)

Autosomal recessive polycystic kidney disease (ARPKD) is one of the most common hereditary renal cystic diseases in children. The clinical spectrum ranges from stillbirth and neonatal demise to survival into adulthood. In a given family, however, patients usually display comparable phenotypes. Many families who lost a child with severe ARPKD desire an early and reliable prenatal diagnosis (PD). Given the limitations of antenatal ultrasound, this is only feasible by molecular genetics that became possible in 1994 when PKHD1, the locus for ARPKD, was mapped to chromosome 6p. However, linkage analysis might prove difficult or even impossible in families with diagnostic doubts or in whom no DNA of an affected child is available. In such cases the recent identification of the PKHD1 gene provides the basis for direct mutation testing. However, due to the large size of the gene, lack of knowledge of the encoded protein's functional properties, and the complicated pattern of splicing, significant challenges are posed by PKHD1 mutation analysis. Thus, it is important to delineate the mutational spectrum and the reachable mutation detection rate among the cohort of severely affected ARPKD patients. In the present study, we performed PKHD1 mutation screening by DHPLC in a series of 40 apparently unrelated families with at least one peri- or neonatally deceased child. We observed 68 out of an expected 80 mutations, corresponding to a detection rate of 85%. Among the mutations identified, 23 were not reported previously. We disclosed two underlying mutations in 29 families and one in 10 cases. Thus, in all but one family (98 percent;), we were able to identify at least one mutation substantiating the diagnosis of ARPKD. Approximately two-thirds of the changes were predicted to truncate the protein. Missense mutations detected were nonconservative, with all but one of the affected amino acid residues found to be conserved in the murine ortholog. PKHD1 mutation analysis has proven to be an efficient and effective means to establish the diagnosis of ARPKD.     

New options for prenatal diagnosis in autosomal recessive polycystic kidney disease by mutation analysis of the PKHD1 gene

Due to the poor prognosis of severe autosomal recessive polycystic kidney disease (ARPKD), there is a strong demand for prenatal diagnosis (PD). Reliable PD testing is possible by molecular genetic analysis only. Although haplotype-based analysis is feasible in most cases, it is associated with a risk of misdiagnosis in families without pathoanatomically proven diagnosis. Linkage analysis is impossible in families where DNA of the index patient is not available. Direct mutation analysis of the recently identified polycystic kidney and hepatic disease 1 gene opens new options in families to whom a reliable PD cannot be offered on the basis of linkage analysis. We for the first time report two cases with PD based on mutation detection, illustrating the new options for PD in ARPKD.     

Course of autosomal recessive polycystic kidney disease (ARPKD) in siblings: a clinical comparison of 20 sibships

Forty-two children out of 20 sibships with autosomal recessive polycystic kidney disease were observed pro- and retrospectively over a mean period of 3.7 years in a long-term study on cystic kidney diseases in children. The intra- and interfamilial variability in terms of age at diagnosis, administration of antihypertensive therapy, liver affection, and renal function were evaluated. According to the 1971 subclassification of Blyth & Ockenden, defining different grades of severity, 12 patients were assigned to the perinatal, nine to the neonatal, 13 to the infantile, and eight to the juvenile subtype of autosomal recessive polycystic kidney disease. In 11 of the 20 families different subtypes were observed among affected siblings. In seven families, affected sibs belonged to adjacent subtypes, while major intrafamilial differences were observed in only four families. The defined subtypes, therefore, cannot be regarded as appropriate in distinguishing genetic groups of autosomal recessive polycystic kidney disease. With respect to the severity of autosomal recessive polycystic kidney disease, there is a wide spectrum of phenotypic manifestations, ranging from stillbirths to mildly affected adults, while intrafamilial variability of the clinical picture is generally small with multiple allelism as the most likely genetic explanation. Age at death, however, showed gross variation in eight sibships. Differences in the clinical course between several siblings cannot be explained by a sex influence in autosomal recessive polycystic kidney disease.     

小儿常染色体隐性遗传多囊肾病临床分析

目的探讨小儿常染色体隐性遗传多囊肾病（autosomal recessive polycystic kidney disease，ARPKD）的临床特点。方法回顾我院1995年1月～2006年12月收治的16例小儿ARPKD的临床资料。结果16例ARPKD中，男11例，女5例，影像学诊断14例，病理学诊断2例，肾脏影像学显示囊肿广泛分布于皮质和髓质。起病时以泌尿系症状就诊仅7例（43．75％），以肾脏外症状就诊3例（18．75％），其他就诊原因包括早产1例，出生时重度窒息1例，血尿素氮-肌酐（Bun—Cr）升高2例，贫血1例，外伤后肾囊肿破裂性腹痛1例。确诊时有12例（75％）肾衰竭，8例（50％）生长迟缓，10例（62．5％）合并肾脏外病变。随诊8例，4例死亡（分别死于先天性肺发育不良、重度窒息后多器官功能衰竭、进行性肾衰竭以及终末期肾病合并胆管细胞癌肾脏转移），1例透析，1例肾移植，1例肾功能正常，1例肝硬化。结论ARPKD为先天遗传性、进行性的肾脏和肝脏损害，小儿期临床表现形式多样，产前诊断对减少ARPKD畸形儿的出生有重要意义。     

Initial evaluation of hepatic T1 relaxation time as an imaging marker of liver disease associated with autosomal recessive polycystic kidney disease (ARPKD)

Autosomal recessive polycystic kidney disease (ARPKD) is a potentially lethal multi‐organ disease affecting both the kidneys and the liver. Unfortunately, there are currently no non‐invasive methods to monitor liver disease progression in ARPKD patients, limiting the study of potential therapeutic interventions. Herein, we perform an initial investigation of T₁ relaxation time as a potential imaging biomarker to quantitatively assess the two primary pathologic hallmarks of ARPKD liver disease: biliary dilatation and periportal fibrosis in the PCK rat model of ARPKD. T₁ relaxation time results were obtained for five PCK rats at 3 months of age using a Look–Locker acquisition on a Bruker BioSpec 7.0 T MRI scanner. Six three‐month‐old Sprague‐Dawley (SD) rats were also scanned as controls. All animals were euthanized after the three‐month scans for histological and biochemical assessments of bile duct dilatation and hepatic fibrosis for comparison. PCK rats exhibited significantly increased liver T₁ values (mean ± standard deviation = 935 ± 39 ms) compared with age‐matched SD control rats (847 ± 26 ms, p = 0.01). One PCK rat exhibited severe cholangitis (mean T₁ = 1413 ms), which occurs periodically in ARPKD patients. The observed increase in the in vivo liver T₁ relaxation time correlated significantly with three histological and biochemical indicators of biliary dilatation and fibrosis: bile duct area percent (R = 0.85, p = 0.002), periportal fibrosis area percent (R = 0.82, p = 0.004), and hydroxyproline content (R = 0.76, p = 0.01). These results suggest that hepatic T₁ relaxation time may provide a sensitive and non‐invasive imaging biomarker to monitor ARPKD liver disease. Copyright © 2015 John Wiley & Sons, Ltd.     

Autosomal dominant polycystic kidney disease in the fetus

We report on 3 cases with a fetal presentation of autosomal dominant polycystic kidney disease (ADPKD), which illustrate the variable expression of ADPKD during fetal life. Fetus 1 was diagnosed at 20 weeks of gestation by ultrasonography; a molecular prenatal diagnosis was performed at 10 weeks on fetus 2, a sib of fetus 1; and ADPKD was an incidental finding in fetus 3 who was aborted at 16 weeks for anencephaly. All pregnancies were terminated and pathologic studies of the fetal kidneys were performed. From these cases and a review of the literature, we draw the following conclusions: (1) so far, all fetal ADPKD kidneys that have been histologically studied have shown cystic dilatations; 28/32 of these fetuses had ultrasonographic manifestations of the disease and/or had sibs with an early-onset form of it; (2) these cysts can be found in newly formed nephrons (fetus 2), predominantly in the more mature nephrons of the deep cortex (fetus 1) or more sparsely distributed in the cortex (fetus 3); these different patterns may reflect different rates of progression of the disease; (3) in contrast to the histologic findings in adult kidneys, glomeruli seem to be predominantly affected in fetal ADPKD; (4) severe fetal expression of ADPKD seems to cluster in some families; and (5) so far, all DNA analyses performed in families with subjects presenting during the fetal or neonatal period have been consistent with linkage to the PKD1 locus. © 1994 Wiley-Liss, Inc.     

Prenatal ultrasonographic findings of dominant polycystic kidney disease and postnatal renal evolution

Autosomal dominant polycystic kidney disease (ADPKD) is a relatively common genetic disorder, and its prenatal diagnosis has been reported with increasing frequency. Nevertheless, no data are available on the significance of prenatal ultrasound (US) patterns in predicting postnatal renal function and outcome. We report on one case of ADPKD diagnosed prenatally by US, and on two cases diagnosed immediately after birth, with different prenatal US and renal outcomes. Data on prenatal US findings and postnatal renal evolution are scanty and largely incomplete. Apparently, none of the prenatal findings are consistently different in cases with and without normal postnatal renal function and blood pressure. More complete information on prenatal US findings and postnatal renal evolution is urgently needed. © 1996 Wiley-Liss, Inc.     

Molecular basis of autosomal recessive polycystic kidney disease (ARPKD)

Autosomal recessive polycystic kidney disease (ARPKD) is a serious genetic disease characterized by cystic changes in the collecting ducts of the kidney and bile ducts within the liver. The gene for ARPKD (PKHD1) is located on chromosome 6p12 and encodes a protein called fibrocystin/polyductin (FPC), 1 of many proteins that are normally present at the primary cilia of the renal tubules and intrahepatic bile ducts. The severity of the clinical disease depends on the type of genetic mutations. Although exact function of FPC is not fully known, it is generally felt that like many of the other ciliary proteins, it plays a vital role in maintaining the structural integrity of organs such as kidney and liver, by modulating important cellular functions, including proliferation, secretion, apoptosis, and terminal differentiation. FPC probably works in conjunction with cellular proteins involved in autosomal dominant polycystic kidney disease that is, polycystin-1 and polycystin-2, which are also located in the primary cilia. Genetic abnormalities in PKHD1 may result in structural and functional abnormalities of FPC, leading to cystic phenotype.     

Hepatorenal findings in obligate heterozygotes for autosomal recessive polycystic kidney disease

Autosomal recessive polycystic kidney disease (ARPKD), characterized by progressive cystic degeneration of the kidneys and congenital hepatic fibrosis (CHF), is the most common childhood onset ciliopathy, with an estimated frequency of 1 in 20,000 births. It is caused by mutations in PKHD1. The carrier frequency for ARPKD in the general population is estimated at 1 in 70. Given the recessive inheritance pattern, individuals who are heterozygous for PKHD1 mutations are not expected to have clinical findings. We performed ultrasound (USG) evaluations on 110 parents from 64 independent ARPKD families and identified increased medullary echogenicity in 6 (5.5%) and multiple small liver cysts in 10 parents (9%). All ARPKD parents with these abnormal imaging findings were asymptomatic; kidney and liver function tests were unremarkable. Complete sequencing of PKHD1 in the 16 ARPKD parents with abnormal imaging confirmed the mutation transmitted to the proband, but did not reveal any other pathogenic variants. Our data suggest that carrier status for ARPKD is a predisposition to polycystic liver disease and renal involvement associated with increased medullary echogenicity on USG. Whether some of these individuals become symptomatic as they age remains to be determined.     

Autosomal recessive polycystic kidney disease

 Autosomal recessive polycystic kidney disease (ARPKD) is a rare inherited disorder which usually becomes clinically manifest in early childhood, although the spectrum of ARPKD is much more variable than generally known. Presentation of ARPKD at later ages and survival into adulthood have been observed in many cases. The responsible gene has been mapped to chromosome 6p. Thus there is no evidence of genetic heterogeneity. The most important indication for DNA diagnosis is the prenatal diagnosis in families with at least one affected child. The critical region has been narrowed with the use of recombinant families of about 4 cM. Several possible candidate genes have been excluded. Received: 23 April 1997 / Accepted: 12 August 1997     

用与PKD2紧密连锁的微卫星DNA对2型常染色体显性多囊肾病进行基因诊断

目的　应用DKD2紧密连锁的微卫星DNA对 2型染色体显性多囊肾病进行基因诊断。方法应用聚合酶链反应 毛细管电泳 基因扫描方法对PKD2基因侧翼微卫星D4S15 3 4、D4S15 42、D4S15 63、D4S2 460和D4S42 3进行基因分型 ,对常染色体显性多囊肾病家系成员进行连锁分析 ,确定患病家系是否与PKD2连锁 ,并对未发病成员进行基因诊断。结果　通过连锁分析 2 0个家系 ,寻找到 3个与PKD2连锁的多囊肾病家系 ;在 3个家系的 4名未发病成员中发现 2例携带PKD2基因突变的症状前个体。结论　连锁分析是多囊肾病异质性研究和基因诊断的一种快速、简便的方法。     

Caroli's syndrome with autosomal recessive polycystic kidney disease in a two month old infant

Caroli's syndrome is a rare congenital disorder that involves intrahepatic bile duct ectasia and congenital hepatic fibrosis, frequently seen with concomitant autosomal recessive polycystic kidney disease (ARPKD). Literature on infants with ARPKD is rare. Here, we present a case of a two month old boy who was diagnosed with Caroli's syndrome and ARPKD.     

Linkage analysis for the diagnosis of autosomal dominant polycystic kidney disease, and for the determination of genetic heterogeneity in Italian families

Sixty-eight individuals from six Italian families in which autosomal dominant polycystic kidney disease (ADPKD) is segregating, were typed in DNA polymorphisms linked to the PKD1 locus on chromosome 16. A total of ten probes were used: 3' HVR, HMJ1, EKMDA, GGG1, 26-6, VK5B, 218EP6, 24.1, CRI090, and 41.1. Zmax was 4.502 at theta = 0.082 between ADPKD and 3'HVR, and 4.382, 1.947, and 1.576 between ADPKD and GGG1, 26.6, and 218EP6, respectively, at theta = 0.0. No clear evidence of genetic heterogeneity was found. Multipoint analyses were consistent with linkage to PKD1. Twenty-nine diagnoses and 16 exclusions made by ultrasonography were confirmed by genotype determinations; in two clinically uncertain cases, DNA analysis predicted one individual as being affected and the other unaffected.     

The attitude of Japanese physicians regarding genetic service for autosomal dominant polycystic kidney disease (ADPKD)

Summary A questionnaire carried out among Japanese physicians revealed that a strong demand for genetic counseling among patients and families with autosomal dominant polycystic kidney disease (ADPKD). In contrast, the awareness of physicians regarding genetic counseling for the disease seemed to be low. For example, 66.0% of the respondents to the questionnaire revealed a negative attitude to providing genetic counseling for patients, and 30.7% of the respondents did not know that most types of polycystic kidney disease are inherited disorders. With the advance of scientific research, the demand for genetic counseling among patients is bound to increase. Therefore, the providers of genetic counseling including the physicians are now pressed to improve their services.     

两个中国常染色体显性遗传性多囊肾病家系的表型与基因型分析

目的研究中国人多囊肾病基因1（polycystic kidney disease 1 gene，PKD1）突变的特点，检测基因突变位点。方法25例多囊肾患者，正常对照16名，扩增PKD1基因的第44、45外显子的基因片段，变性梯度凝胶电泳突变检测系统进行初筛，然后测序。结果发现1个移码突变（12431delCT）、1个无义突变（C12217T）、1个多态性（A50747C），突变检测率为8％（2／25）。结论检测到2个新的可能的致病突变：1个移码突变（12431delCT）、1个无义突变（C12217T）。     

Apparent normalisation of fetal renal size in autosomal dominant polycystic kidney disease (PKD1)

We present a family with adult onset autosomal dominant polycystic kidney disease (ADPKD) in two generations, linked to the PKD1 locus and with paternal transmission to the fetus. The fetus carried the PKD1 haplotype and was, therefore a gene carrier. Progressive hyperechogenic renal enlargement, but no cysts, was documented by serial fetal ultrasounds at 21, 23 and 34 weeks of gestation. Surprisingly, the newborn renal scan showed normal sized kidneys with apparently normal corticomedullary differentiation. However, at 11 months of age, the evolution of cysts in one kidney, and then in the other kidney at 20 months, was documented by ultrasound in the absence of clinical symptoms or signs. The observed normalisation of fetal renal ultrasound appearances at birth has not previously been described in fetuses presenting with PKD1.