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Multiple genes and their variants that lend susceptibility to many diseases will play a major role in clinical routine. Genetics-based cost reduction strategies in diagnostic processes are important in the setting of multiple susceptibility genes for a single disease. Head and neck paraganglioma (HNP) is caused by germline mutations of at least three succinate dehydrogenase subunit genes (SDHx). Mutation analysis for all 3 costs ∼US$2,700 per patient. Genetic classification is essential for downstream management of the patient and preemptive management of family members. Utilizing HNP as a model, we wanted to determine predictors to prioritize the most heritable clinical presentations and which gene to begin testing in HNP presentations, to reduce costs of genetic screening. Patients were tested for SDHB, SDHC, and SDHD intragenic mutations and large deletions. Clinical parameters were analyzed as potential predictors for finding germline mutations. Cost reduction was calculated between prioritized gene testing compared with that for all genes. Of 598 patients, 30.6% had SDHx germline mutations: 34.4% in SDHB, 14.2% SDHC, and 51.4% SDHD. Predictors for an SDHx mutation are family history [odds ratio (OR), 37.9], previous pheochromocytoma (OR, 10.9), multiple HNP (OR, 10.6), age ≤40 years (OR, 4.0), and male gender (OR, 3.5). By screening only preselected cases and a stepwise approach, 60% cost reduction can be achieved, with 91.8% sensitivity and 94.5% negative predictive value. Our data give evidence that clinical parameters can predict for mutation and help prioritize gene testing to reduce costs in HNP. Such strategy is cost-saving in the practice of genetics-based personalized health care. [Cancer Res 2009;69(8):3650–6]

Supplementary Table 1 Legends and References from Clinical Predictors for Germline Mutations in Head and Neck Paraganglioma Patients: Cost Reduction Strategy in Genetic Diagnostic Process as Fall-Out

Supplementary Table 1 from Clinical Predictors for Germline Mutations in Head and Neck Paraganglioma Patients: Cost Reduction Strategy in Genetic Diagnostic Process as Fall-Out

Other Supporting Colleagues from Clinical Predictors for Germline Mutations in Head and Neck Paraganglioma Patients: Cost Reduction Strategy in Genetic Diagnostic Process as Fall-Out

Supplementary Table 2 from Clinical Predictors for Germline Mutations in Head and Neck Paraganglioma Patients: Cost Reduction Strategy in Genetic Diagnostic Process as Fall-Out

By implementation of non-invasive prenatal testing (NIPT) for the diagnosis of Down syndrome (DS) in maternity care, an ethical debate is newly inflamed how to deal with this information. Fears of the consequences of an increased use of NIPT are justified with the same arguments when amniocentesis and preimplantation genetic diagnosis (PGD) were introduced decades ago. It can be expected that the prevalence of people with DS would significantly increase in Western societies as a result of the increasing age of pregnant women and the improved medical care for people with DS. The net effect as to whether an increasing uptake of NIPT will result in more abortions of fetuses with trisomy 21 cannot be reliably estimated. This holds true since more and more couples will use results of NIPT for information only, but will not opt for termination of pregnancy. Although parents love their children with DS, in a society where reproductive autonomy is seen as an achievement, access to NIPT cannot be limited. On this background, comprehensive and qualified pretest counseling is vital, also to avoid possible stigmatization of people with DS and as the resulting consequence to avoid feared deterioration in their living conditions, for which, however, there is no evidence to date. The personal view of a mother of a child with DS illustrates the complexity in dealing with NIPT, which does not allow simple answers and must be understood as a challenge for society as a whole.

Autosomal recessive polycystic kidney disease (ARPKD) is a severe disease of early childhood that is clinically characterized by fibrocystic changes of the kidneys and the liver. The main cause of ARPKD are variants in the PKHD1 gene encoding the large transmembrane protein fibrocystin. The mechanisms underlying the observed clinical heterogeneity in ARPKD remain incompletely understood, partly due to the fact that genotype-phenotype correlations have been limited to the association of biallelic null variants in PKHD1 with the most severe phenotypes. In this observational study we analyzed a deep clinical dataset of 304 patients with ARPKD from two independent cohorts and identified novel genotype-phenotype correlations during childhood and adolescence. Biallelic null variants frequently show severe courses. Additionally, our data suggest that the affected region in PKHD1 is important in determining the phenotype. Patients with two missense variants affecting amino acids 709-1837 of fibrocystin or a missense variant in this region and a null variant less frequently developed chronic kidney failure, and patients with missense variants affecting amino acids 1838-2624 showed better hepatic outcome. Variants affecting amino acids 2625-4074 of fibrocystin were associated with poorer hepatic outcome. Thus, our data expand the understanding of genotype-phenotype correlations in pediatric ARPKD patients and can lay the foundation for more precise and personalized counselling and treatment approaches. German Society for Pediatric Nephrology (GPN); ESCAPE Network; European Society for Paediatric Nephrology (ESPN); German PKD foundation; Koeln Fortune program; GEROK program of the Medical Faculty of University of Cologne; Marga and Walter Boll-Foundation; German Federal Ministry of Research and Education (BMBF)Federal Ministry of Education & Research (BMBF) [01GM1515, 01GM1903]; working group CAKUT of the ESPN; working group Inherited Kidney Diseases of the ESPN We thank the German Society for Pediatric Nephrology (GPN) and the ESCAPE Network for their support. We thank Mr Mathias Burgmaier (Aachen) and Mr Samuel Kilian (Heidelberg) for support in conducting statistical analysis. ML was supported by grants of the GPN, the European Society for Paediatric Nephrology (ESPN), the German PKD foundation, the Koeln Fortune program, the GEROK program of the Medical Faculty of University of Cologne, and the Marga and Walter Boll-Foundation. FS, CB, and ML are supported by the German Federal Ministry of Research and Education (BMBF grant 01GM1515 and 01GM1903). KB was supported by the Koeln Fortune program and the GEROK program of the Medical Faculty of University of Cologne, as well as the Marga and Walter Boll-Foundation. This work was generated within the European Reference Network for Rare Kidney Disorders (ERKNet). The work was supported by the working groups CAKUT and Inherited Kidney Diseases of the ESPN.

With the Act on Genetic Testing (GenDG), the German legislator has issued far-reaching regulations for human genetic services, including genetic counseling. This paper presents data on the use of human genetic counseling in the years before and after the entry into force of GenDG in order to provide an informed assessment of the possible effects of the law.Over a period of 13 years (2005 to 2017), the human genetic counseling services provided within the framework of the statutory health insurance and billable by EBM via the Kassenärztliche associations were recorded via a database query at the Central Institute of the National Association of Statutory Health Insurance Physicians (ZI-KBV) and via individual Kassenärztliche Vereinigungen Deutschlands. For the discussion of the observable development of using genetic counseling and possible future development, additional data on the referral behavior, the waiting times, processing time, and reasons for consultations were extracted from the GenBIn database.Demand for genetic counseling has steadily increased at an average rate of approximately 6% per year since 2009. This increase started well before the enactment of the GenDG and may be attributed to a multiplicity of factors. Change in demand for genetic counseling is characterized by increasing self-referrals and by increasing referrals by specialists other than obstetricians/gynecologists. Waiting times between 2011 and 2016/2017 have increased. While demand has been growing, the number of key service providers, the contracted medical specialists in human genetics, has remained almost constant. It is foreseeable that capacity limits will be reached if both trends continue.

Every year, about 60 000 people in Germany contract colo-rectal carcinoma. Hereditary factors are the cause in approx. 5 % and those affected often fall ill at a young age. Often there are concrete indications of an individual high risk in affected families. The identification of persons at risk enables a targeted early detection and prevention of cancer as an important interdisciplinary medical task. The current AWMF guideline "Colorectal carcinoma" makes concrete statements in this regard.

De novo pathogenic variants in CNOT3 have recently been reported in a developmental delay disorder (intellectual developmental disorder with speech delay, autism, and dysmorphic facies [IDDSADF, OMIM: #618672]). The patients present with a variable degree of developmental delay and behavioral problems. To date, all reported disease-causing variants occurred de novo and no parent-child transmission was observed. We report for the first time autosomal dominant transmissions of the CNOT3-associated developmental disorder in two unrelated families. The clinical characteristics in our patients match the IDDSADF features reported so far and suggest substantial variability of the phenotype within the same family.

Every year, about 60 000 people in Germany contract colo-rectal carcinoma. Hereditary factors are the cause in approx. 5 % and those affected often fall ill at a young age. Often there are concrete indications of an individual high risk in affected families. The identification of persons at risk enables a targeted early detection and prevention of cancer as an important interdisciplinary medical task. The current AWMF guideline "Colorectal carcinoma" makes concrete statements in this regard.

By using the example of hearing loss, an overview is given on genetics, new diagnostic developments and their applications. Owing to novel high-throughput technologies of DNA sequencing, most patients now can get a genetic diagnosis for several reasons, in the routine workup after failed newborn hearing screening but also in cases of hearing loss manifesting later in life.

INTRODUCTION A gene-environment interaction between expression genotypes of the monoamine oxidase A (MAOA) and adverse childhood experience increases the risk of antisocial behavior. However, the neural underpinnings of this interaction remain uninvestigated. A cortico-limbic circuit involving the prefrontal cortex (PFC) and the amygdala is central to the suppression of aggressive impulses and is modulated by serotonin (5-HT). MAOA genotypes may modulate the vulnerability of this circuit and increase the risk for emotion regulation deficits after specific life events. Acute tryptophan depletion (ATD) challenges 5-HT regulation and may identify vulnerable neuronal circuits, contributing to the gene-environment interaction. METHODS Functional magnetic resonance imaging measured the resting-state state activity in 64 healthy males in a double-blind, placebo-controlled study. Cortical maps of amygdala correlation identified the impact of ATD and its interaction with low- (MAOA-L) and high-expression variants (MAOA-H) of MAOA on cortico-limbic connectivity. RESULTS Across all Regions of Interest (ROIs) exhibiting an ATD effect on cortico-limbic connectivity, MAOA-L carriers were more susceptible to ATD than MAOA-H carriers. In particular, the MAOA-L group exhibited a larger reduction of amygdala connectivity with the right prefrontal cortex and a larger increase of amygdala connectivity with the insula and dorsal PCC. CONCLUSION MAOA-L carriers were more susceptable to a central 5-HT challenge in cortico-limbic networks. Such vulnerability of the cortical serotonergic system may contribute to the emergence of antisocial behavior after systemic challenges, observed as gene-environment interaction. Hum Brain Mapp 38:1622-1635, 2017. © 2016 Wiley Periodicals, Inc.

Zusammenfassung Die rechtlichen Regelungen der Präimplantationsdiagnostik (PID) in Europa sind sehr heterogen. In der Folge unterscheidet sich die Praxis der PID erheblich. Während einzelne Länder wie England auf eine sehr lange Praxis zurückblicken können, sind die rechtlichen Rahmenbedingungen in anderen Ländern wie Deutschland oder der Schweiz erst in den letzten Jahren geschaffen worden, sodass die Erfahrungen aus diesen Ländern sehr begrenzt sind. Das Präimplantationsdiagnostik Consortium der European Society of Human Reproduction and Embryology (ESHRE) hat die Erfahrungen mit der PID von fast 20 Jahren vorbildlich dokumentiert und regelmäßig ausgewertet, sodass umfassende Daten zur Praxis der PID verfügbar sind. Mit dem vorliegenden Beitrag soll für ausgewählte Aspekte ein Überblick über den Stand der PID in Europa gegeben werden, der aufgrund der sehr heterogenen Regelungen keinen Anspruch auf Vollständigkeit erheben kann.

Der nicht-invasive molekulargenetische Test (NIPT) zum Vorliegen von Trisomien wird voraussichtlich ab Herbst 2020 Kassenleistung. Dieser Bluttest stellt eine ungefahrliche Alternative zur risikoreichen Amniozentese dar. Kritiker erheben jedoch ethische Einwande. Wie sollten wir NIPT handhaben?

Disturbed mitochondrial fusion and fission have been linked to various neurodegenerative disorders. In siblings from two unrelated families who died soon after birth with a profound neurodevelopmental disorder characterized by pontocerebellar hypoplasia and apnoea, we discovered a missense mutation and an exonic deletion in the SLC25A46 gene encoding a mitochondrial protein recently implicated in optic atrophy spectrum disorder. We performed functional studies that confirmed the mitochondrial localization and pro-fission properties of SLC25A46. Knockdown of slc24a46 expression in zebrafish embryos caused brain malformation, spinal motor neuron loss, and poor motility. At the cellular level, we observed abnormally elongated mitochondria, which was rescued by co-injection of the wild-type but not the mutant slc25a46 mRNA. Conversely, overexpression of the wild-type protein led to mitochondrial fragmentation and disruption of the mitochondrial network. In contrast to mutations causing non-lethal optic atrophy, missense mutations causing lethal congenital pontocerebellar hypoplasia markedly destabilize the protein. Indeed, the clinical severity appears inversely correlated with the relative stability of the mutant protein. This genotype-phenotype correlation underscores the importance of SLC25A46 and fine tuning of mitochondrial fission and fusion in pontocerebellar hypoplasia and central neurodevelopment in addition to optic and peripheral neuropathy across the life span.

Introduction Heterozygous BICD2 gene mutations cause a form of autosomal dominant spinal muscular atrophy with lower extremity predominance (SMALED). Methods We analyzed the BICD2 gene in a selected group of 25 index patients with neurogenic muscle atrophy. Results We identified 2 new BICD2 missense mutations, c.2515G>A, p.Gly839Arg, in a family with autosomal dominant inheritance, and c.2202G>T, p.Lys734Asn, as a de novo mutation in an isolated patient with similar phenotype. The patients had congenital foot contractures, muscle atrophy of the legs, and slowly progressive weakness of the shoulder girdle. There was no apparent sensory or brain dysfunction. One patient died of unrelated reasons at age 52 years. Autopsy revealed no upper motor neuron and only moderate lower motor neuron loss, but there was distal corticospinal tract degeneration and marked neurogenic muscular atrophy. Conclusion These findings give further insight into the clinical and pathoanatomical consequences of BICD2 mutations. Muscle Nerve 54: 496–500, 2016

Silver-Russell syndrome (SRS) is a growth retardation syndrome characterized by intrauterine and postnatal growth retardation, relative macrocephaly and protruding forehead, body asymmetry and feeding difficulties. Nearly 50% of cases show a hypomethylation in 11p15.5, in 10% maternal uniparental disomy of chromosome 7 is present. A significant number of patients with SRS features also exhibit chromosomal aberrations. We analyzed 43 individuals referred for SRS genetic testing by molecular karyotyping. Pathogenic variants could be detected in five of them, including a NSD1 duplication in 5q35 and a 14q32 microdeletion. NSD1 deletions are detectable in overgrowth disorders (Sotos syndrome and Beckwith-Wiedemann syndrome), whereas NSD1 duplications are associated with growth retardation. The 14q32 deletion is typically associated with Temple syndrome (TS14), but the identification of a patient in our cohort reflects the clinical overlap between TS14 and SRS. As determination of molecular subtypes is the basis for a directed counseling and therapy, the identification of pathogenic variants in >10% of the total cohort of patients referred for SRS testing and in >16% of characteristic individuals with the characteristic SRS phenotype confirms the need to apply molecular karyotyping in this cohort.

Background: There are only few reports of pregnancy and delivery in non-dystrophic myotonia or periodic paralysis caused by CLCN1 or SCN4A gene mutations. Methods: We report the medical histories and personal attitudes of 5 unrelated German patients, 2 following autosomal recessive inheritance (case 1; most likely and case 2; confirmed Becker disease) and 3 following autosomal dominant inheritance (case 3; CLCN1 mutation, cases 4-5; SCN4A mutations), who delivered a total of 9 children. Results: Apart from case 5 with periodic paralysis, who had 5 early miscarriages and pre-eclampsia resulting in cesarean delivery, there was no evidence of increased obstetric complication rates, and neonatal outcome was favorable. In all patients, there was aggravation of myotonia or weakness in pregnancy, followed by a short-term improvement after delivery in cases 2 and 3. Mexiletine medication improved the clinical features significantly in case 2 but was unable to control pregnancy-related deterioration. In case 4 (and her sister) and case 5, there was a clear disease aggravation in pregnancy resulting in hospitalization or repeated neurological examinations. Conclusion: Pregnancy can be regarded as a strong triggering factor in inherited non-dystrophic myotonias and periodic paralysis, regardless of the underlying gene defect.

OBJECTIVE: To identify prenatal, perinatal, and postnatal risk factors for dialysis within the first year of life in children with autosomal recessive polycystic kidney disease (ARPKD) as a basis for parental counseling after prenatal and perinatal diagnosis. STUDY DESIGN: A dataset comprising 385 patients from the ARegPKD international registry study was analyzed for potential risk markers for dialysis during the first year of life. RESULTS: Thirty-six out of 385 children (9.4%) commenced dialysis in the first year of life. According to multivariable Cox regression analysis, the presence of oligohydramnios or anhydramnios, prenatal kidney enlargement, a low Apgar score, and the need for postnatal breathing support were independently associated with an increased hazard ratio for requiring dialysis within the first year of life. The increased risk associated with Apgar score and perinatal assisted breathing was time-dependent and vanished after 5 and 8 months of life, respectively. The predicted probabilities for early dialysis varied from 1.5% (95% CI, 0.5%-4.1%) for patients with ARPKD with no prenatal sonographic abnormalities to 32.3% (95% CI, 22.2%-44.5%) in cases of documented oligohydramnios or anhydramnios, renal cysts, and enlarged kidneys. CONCLUSIONS: This study, which identified risk factors associated with onset of dialysis in ARPKD in the first year of life, may be helpful in prenatal parental counseling in cases of suspected ARPKD. ispartof: JOURNAL OF PEDIATRICS vol:199 pages:22-+ ispartof: location:United States status: published

We present clinical features and genetic results of 1206 index patients and 124 affected relatives who were referred for genetic testing of Charcot-Marie-Tooth (CMT) neuropathy at the laboratory in Aachen between 2001 and 2012. Genetic detection rates were 56% in demyelinating CMT (71% of autosomal dominant (AD) CMT1/CMTX), and 17% in axonal CMT (24% of AD CMT2/CMTX). Three genetic defects (PMP22 duplication/deletion, GJB1/Cx32 or MPZ/P0 mutation) were responsible for 89.3% of demyelinating CMT index patients in whom a genetic diagnosis was achieved, and the diagnostic yield of the three main genetic defects in axonal CMT (GJB1/Cx32, MFN2, MPZ/P0 mutations) was 84.2%. De novo mutations were detected in 1.3% of PMP22 duplication, 25% of MPZ/P0, and none in GJB1/Cx32. Motor nerve conduction velocity was uniformly 40 m/s in MFN2, and more variable in GJB1/Cx32, MPZ/P0 mutations. Patients with CMT2A showed a broad clinical severity regardless of the type or position of the MFN2 mutation. Out of 75 patients, 8 patients (11%) with PMP22 deletions were categorized as CMT1 or CMT2. Diagnostic algorithms are still useful for cost-efficient mutation detection and for the interpretation of large-scale genetic data made available by next generation sequencing strategies.

Nicht-invasive genetische Pranataltests erlauben heute mit hoher Zuverlassigkeit die Identifizierung von Schwangerschaften mit kindlichen Aneuploidien. Durch die prinzipielle Verfugbarkeit der Tests fur alle Schwangeren wirft das Testangebot eine Vielzahl ethischer Fragen auf, deren Beantwortung nur in einen gesamtgesellschaftlichen Diskurs moglich ist.

AIMS: A link between alcohol use disorders (AUD) and impulsivity is well established. As there is evidence for the heritability of AUD, the investigation of the underlying genetic disposition for both conditions is an important issue. An association between AUD and a coding single nucleotide polymorphism (SNP) (rs1799971 encoding an Asn40Asp amino acid substitution, A118G) within the µ-opioid receptor 1 gene (OPRM1) has been reported. Therefore we tested the association between the OPRM1 A118G polymorphism and drinking as well as impulsive behavior in social drinkers. METHODS: A total of 214 healthy male social drinkers were recruited. Each participant was genotyped for the OPRM1 A118G variant. Alcohol use was assessed with items of the Alcohol Use Disorders Identification Test (AUDIT). Impulsivity was assessed using the UPPS impulsive behavior scale. For statistical analyses, we considered correlations, t-tests and ordinal regression models using SPSS V21. RESULTS: In total, 49 out of 214 participants were carriers of the OPRM1 118G allele. On average the OPRM1 118G carriers showed a slightly higher propensity for alcohol drinking. Higher drinking frequency among the G allele carriers was linked with higher urgency and perseveration subscores of impulsivity. CONCLUSION: Our results suggest a genetically influenced higher propensity for alcohol drinking among social drinkers carrying the 118G allele of the OPRM1 gene. The positive correlation between urgency and a higher drinking frequency among the OPRM1 118G hint towards a functional meaning of the opioid system in the regulation of impulsivity. Language: en

OBJECTIVE: An association between maternal HELLP syndrome and fetal long chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency has been proposed. LCHAD catalyzes the third step in the beta-oxidation of fatty acids in mitochondria. Whereas about 75% of LCHAD-deficient patients carry a G-to-C mutation at nucleotide position 1528 (Glu474Gln, E474Q) on both chromosomes, compound heterozygosity for E474Q on one chromosome and a second different LCHAD mutation on the other can be observed in up to 25% of LCHAD-deficiency cases; only very few patients carry two mutations different from E474Q. Genetic analysis of the mother alone is insufficient in case of compound heterozygosity. Since information on the fetal carrier status of the E474Q mutation in maternal HELLP syndrome is rare, we investigated the frequency of the E474Q mutation in families where the mother had HELLP syndrome. METHODS: The occurrence of the E474Q mutation was analyzed by PCR and RFLP in 103 mothers with HELLP syndrome, in 82 children of affected pregnancies and in 21 fathers in families where fetal DNA was not available. In addition, 103 control women with only uncomplicated pregnancies were investigated. RESULTS: The mutation E474Q was not detected in the study population. CONCLUSION: Neither maternal nor fetal heterozygosity for the E474Q mutation is a relevant factor of HELLP syndrome.

Autosomal recessive polycystic kidney disease (ARPKD), usually considered to be a genetically homogeneous disease caused by mutations in PKHD1, has been associated with ciliary dysfunction. Here, we describe mutations in DZIP1L, which encodes DAZ interacting protein 1-like, in patients with ARPKD. We further validated these findings through loss-of-function studies in mice and zebrafish. DZIP1L localizes to centrioles and to the distal ends of basal bodies, and interacts with septin2, a protein implicated in maintenance of the periciliary diffusion barrier at the ciliary transition zone. In agreement with a defect in the diffusion barrier, we found that the ciliary-membrane translocation of the PKD proteins polycystin-1 and polycystin-2 is compromised in DZIP1L-mutant cells. Together, these data provide what is, to our knowledge, the first conclusive evidence that ARPKD is not a homogeneous disorder and further establish DZIP1L as a second gene involved in ARPKD pathogenesis.

Meckel–Gruber syndrome (MKS, OMIM #607361) is a rare pre- or perinatal lethal autosomal recessive ciliopathy caused by mutations in at least 12 known genes. It has a clinical and genetic overlap with other viable ciliopathies, especially Joubert syndrome and Joubert syndrome-related disorders. MKS is characterized by multicystic kidney dysplasia, central nervous system malformations (usually occipital encephalocele), ductal plate malformation of the liver, and postaxial polydactyly. We identified a homozygous mutation in TMEM67 (MKS3) in a fetus affected by MKS; however, only the mother was a carrier of the respective mutation. Genotyping with polymorphic microsatellite markers and single nucleotide polymorphism (SNP) array revealed a maternal uniparental disomy (UPD) of the entire chromosome 8 (upd(8)mat), harboring TMEM67. This is the first reported case of UPD as a cause of MKS. The possible underlying mechanisms for uniparental disomy (UPD) are reviewed. Even if rare, awareness of UPD and comprehensive work-up in the case of unexpected homozygosity for a recessive mutation is essential for accurate genetic counseling and assessment of the risk of recurrence.

Autosomal recessive polycystic kidney disease (ARPKD) constitutes an important cause of pediatric end stage renal disease and is characterized by a broad phenotypic variability. The disease is caused by mutations in a single gene, Polycystic Kidney and Hepatic Disease 1 (PKHD1), which encodes a large transmembrane protein of poorly understood function called fibrocystin. Based on current knowledge of genotype–phenotype correlations in ARPKD, two truncating mutations are considered to result in a severe phenotype with peri- or neonatal mortality. Infants surviving the neonatal period are expected to carry at least one missense mutation. We report on a female patient with two truncating PKHD1 mutations who survived the first 30 months of life without renal replacement therapy. Our patient carries not only a known stop mutation, c.8011C>T (p.Arg2671*), but also the previously reported c.51A>G PKHD1 sequence variant of unknown significance in exon 2. Using functional in vitro studies we have confirmed the pathogenic nature of c.51A>G, demonstrating activation of a new donor splice site in intron 2 that results in a frameshift mutation and generation of a premature stop codon. This case illustrates the importance of functional mutation analyses and also raises questions regarding the current belief that the presence of at least one missense mutation is necessary for perinatal survival in ARPKD.