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Polycystic kidney disease is a severe genetic disease occurring in both adult and pediatric patients. The basic characteristic of this disease is the development and progressive enlargement of renal cysts gradually replacing functional kidney tissue. This leads to renal failure in many patients. However, renal cysts may also occur in a number of other diseases, including multisystem syndromes. This complicates differential diagnosis in some patients. In our study, we first focused on the diagnosis and characterization of genotypic-phenotypic relationships in patients with polycystic disease arising in childhood, later we extended our study to adult patients and patients with unclear clinical diagnosis. At the same time, we expanded the portfolio of analyzed disorders to a number of diseases in which the phenotype of polycystic kidneys may occur, and noncystic diseases as well. During our project, massive parallel sequencing was used to analyze 149 patients - 128 with cystic and 21 with noncystic clinically diagnosed nephropathies. At the same time, the findings were verified by Sanger sequencing in 176 relatives of our probands. Mutation detection reached 59% in cystic patients, and 43% in non-cystic patients, respectively. In many patients, molecular genetic analysis revealed a different etiology...

Background: Autosomal polycystic kidney disease is distinguished into dominant (ADPKD) and recessive (ARPKD) inheritance usually caused by either monoallelic (PKD1/PKD2) or biallelic (PKHD1) germline variation. Clinical presentations are genotype-dependent ranging from fetal demise to mild chronic kidney disease (CKD) in adults. Additionally, exemptions from dominant and recessive inheritance have been reported in both disorders resulting in respective phenocopies. Here, we comparatively report three young adults with microcystic-hyperechogenic kidney morphology based on unexpected genetic alterations beyond typical inheritance. Methods: Next-generation sequencing (NGS)-based gene panel analysis and multiplex ligation-dependent probe amplification (MLPA) of PKD-associated genes, familial segregation analysis, and reverse phenotyping. Results: Three unrelated individuals presented in late adolescence for differential diagnosis of incidental microcystic-hyperechogenic kidneys with preserved kidney and liver function. Upon genetic analysis, we identified a homozygous hypomorphic PKHD1 missense variant causing pseudodominant inheritance in a family, a large monoallelic PKDH1-deletion with atypical transmission, and biallelic PKD1 missense hypomorphs with recessive inheritance. Conclusion: By this report, we illustrate clinical presentations associated with atypical PKD-gene alterations beyond traditional modes of inheritance. Large monoallelic PKHD1-alterations as well as biallelic hypomorphs of both PKD1 and PKHD1 may lead to mild CKD in the absence of prominent macrocyst formation and functional liver impairment. The long-term renal prognosis throughout life, however, remains undetermined. Increased detection of atypical inheritance challenges our current thinking of disease ontology not only in PKD but also in Mendelian disorders in general.

Autosomal recessive polycystic kidney disease (ARPKD) is a rare severe inherited disease manifested by cystic renal disease, congenital hepatic fibrosis and dilatatation of bile ducts. The spectrum of clinical manifestations is very wide and variable, depends on the age at which the disease was manifested. In severe forms of the disease, it is possible to detect the first symptoms prenatally around the 20th week of pregnancy due to increased echogenic kidneys and the presence of oligohydramnios. The causal gene of this disease is thePKHD1 gene with protein product fibrocystin that is most likely contributing on maintaining the intracellular concentration of Ca2+ cations. The exact phatophysiology mechanism of ARPKD remains unknown. Phenotypic manifestations of this disease may overlap with mutations associated with other genes. One of the genes mimicking the ARPKD phenotype is the HNF1B gene. Mutations associated with HNF1B gene are the most common monogenic cause of developmental kidney abnormalities. HNF1B is a tissue-specific transcription factor that regulates the expression of PKHD1. In experimental part I worked on genetic analysis of the HNF1B gene in 28 patients who have not been confirmed ARPKD diagnosis by detection of 2 PKHD1 mutations. For the purposes of mutational screening, I used...