Comprehensive genetic testing in children with a clinical diagnosis of ARPKD identifies phenocopies

Tamás Szabó, Petronella Orosz, Eszter Balogh, Eszter Jávorszky, István Máttyus, Csaba Bereczki, Zoltán Maróti, Tibor Kalmár, Attila J. Szabó, George Reusz, Ildikó Várkonyi, Erzsébet Marián, Éva Gombos, Orsolya Orosz, László Madar, György Balla, János Kappelmayer, Kálmán Tory, István Balogh

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4 Citations (Scopus)

Abstract

Background: Autosomal recessive polycystic kidney disease (ARPKD) is genetically one of the least heterogeneous ciliopathies, resulting primarily from mutations of PKHD1. Nevertheless, 13–20% of patients diagnosed with ARPKD are found not to carry PKHD1 mutations by sequencing. Here, we assess whether PKHD1 copy number variations or second locus mutations explain these cases. Methods: Thirty-six unrelated patients with the clinical diagnosis of ARPKD were screened for PKHD1 point mutations and copy number variations. Patients without biallelic mutations were re-evaluated and screened for second locus mutations targeted by the phenotype, followed, if negative, by clinical exome sequencing. Results: Twenty-eight patients (78%) carried PKHD1 point mutations, three of whom on only one allele. Two of the three patients harbored in trans either a duplication of exons 33–35 or a large deletion involving exons 1–55. All eight patients without PKHD1 mutations (22%) harbored mutations in other genes (PKD1 (n = 2), HNF1B (n = 3), NPHP1, TMEM67, PKD1/TSC2). Perinatal respiratory failure, a kidney length > +4SD and early-onset hypertension increase the likelihood of PKHD1-associated ARPKD. A patient compound heterozygous for a second and a last exon truncating PKHD1 mutation (p.Gly4013Alafs*25) presented with a moderate phenotype, indicating that fibrocystin is partially functional in the absence of its C-terminal 62 amino acids. Conclusions: We found all ARPKD cases without PKHD1 point mutations to be phenocopies, and none to be explained by biallelic PKHD1 copy number variations. Screening for copy number variations is recommended in patients with a heterozygous point mutation.

Original languageEnglish
Pages (from-to)1713-1721
Number of pages9
JournalPediatric Nephrology
Volume33
Issue number10
DOIs
Publication statusPublished - Oct 1 2018

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Keywords

  • CNV
  • Duplication
  • Phenocopy
  • Polycystic kidney
  • Second locus mutation

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Nephrology

Cite this

Szabó, T., Orosz, P., Balogh, E., Jávorszky, E., Máttyus, I., Bereczki, C., Maróti, Z., Kalmár, T., Szabó, A. J., Reusz, G., Várkonyi, I., Marián, E., Gombos, É., Orosz, O., Madar, L., Balla, G., Kappelmayer, J., Tory, K., & Balogh, I. (2018). Comprehensive genetic testing in children with a clinical diagnosis of ARPKD identifies phenocopies. Pediatric Nephrology, 33(10), 1713-1721. https://doi.org/10.1007/s00467-018-3992-5