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Kidney Week

Abstract: FR-PO804

Sanger Sequencing Pitfall Exists in Hereditary Thrombotic Microangiopathy with Homozygous Mutation Identified in Only One Biological Parent

Session Information

Category: Genetic Diseases of the Kidneys

  • 1002 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Wang, Fang, Peking University First Hospital, Beijing, China
  • Deng, Haiyue, Peking University First Hospital, Beijing, China
  • Zhang, Yanqin, Peking University First Hospital, Beijing, China
  • Yao, Yong, Peking University First Hospital, Beijing, China
  • Ding, Jie, Peking University First Hospital, Beijing, China
Background

The aim of this study was to elucidate the underlying etiology of a mutation appeared to be homozygous which was identified in only one of parents in one boy with hereditary thrombotic microangiopathy.

Methods

One boy was diagnosed as steroid-resistant nephrotic syndrome at 2.4 years old. Urinary protein recurrence occurred 1.5 years later, while serum creatinine (Scr) increased to 83 umol/L and platelet (PLT) decreased to 40×109/L. One point eight years later, hemoglobin (Hb) was 72 g/L, PLT 29×109/L, Scr 120 umol/L. Five point nine years later, his renal function was normal. Light microscopy, electron microscopy and immunofluorescence of renal biopsy indicated thrombotic microangiopathy. Genetic analysis revealed he had homozygous DGKE (NM_003647) missense variant c.1420G>A (p. Asp474Asn) which was identified in only his father. Six short tandem repeats (STR) were selected to confirm biological relationships between the boy and his parents. Quantitative PCR was performed to detect the deletion by Bio-Rad CFX real time PCR system using SYBR Green I qPCR SuperMix (TransGen Biotech, China, AQ131).

Results

Six loci alleles in different chromosomes demonstrated typical Mendelian inheritance with paternal and maternal alleles being detected in the patient, which indicated that biological relationship of the boy and his parents exist. The gDNA quantity in DGKE exon 11 of the boy was half of the normal control while normal in his parents. Further analysis showed the breakpoints in DGKE were exon 1 and exon 12. It may be a de novo heterozygous deletion.

Conclusion

The case was demonstrated to be homozygous due to a large deletion encompassing a missense/small deletion in DGKE gene.

Funding

  • Government Support - Non-U.S.