PB0831 - Novel VWF exon 9-10 duplication in a family with inherited bleeding, high VWF:Ag and FVIII levels, and loss of high molecular weight VWF multimers.

Monday, June 26, 2023

18:30 – 19:30 ET

Room: Exhibition

Presenting Author(s)

Jill M. Johnsen, MD (she/her/hers)

Associate Professor, Division of Hematology
University of Washington, Institute for Stem Cell and Regenerative Medicine, Seattle, WA, USA
Seattle, Washington, United States

Co-Author(s)

JG

Joseph Gasper

Research Scientist
University of Washington
Seattle, Washington, United States
SF

Shelley Fletcher

Genomics Specialist
Bloodworks
Seattle, Washington, United States
KL

Kerry Lannert

Research Scientist
University of Washington
Seattle, Washington, United States
Barbara A. Konkle, MD (she/her/hers)

Professor of Medicine
University of Washington
Seattle, Washington, United States
Rebecca Kruse-Jarres, MD

Professor
University of Washington
Seattle, Washington, United States
DM

Daniel Miller

Assistant Professor
University of Washington
Seattle, Washington, United States

Background: von Willebrand disease (VWD) is characterized by bleeding and VWF deficiency. The highest laboratory cut-off to diagnose VWD is VWF < 50 (all units are IU/dL) per VWD guidelines (James et al. 2021). We studied a family where the proband is consistent with type 2A VWD, except all VWF levels >50 (VWF:Ag 293, VWF:Act 97, VWF:CB 90, FVIII 173, decreased high molecular weight (HMW) multimers). Four relatives span 3 generations with similar lab results. The youngest is the only person with levels < 50 (VWF:Ag 186, VWF:Act 38). VWF genotyping found no causative DNA variants. All affected family members were responsive to VWD treatments.

Aims: To investigate the genetic basis of high VWF levels with loss of VWF multimers in this family.

Methods: The proband and sister gave informed consent. Clinical data were abstracted from the EHR. Short-read DNA sequencing was performed with a custom NGS target (VWD-Seq, 33 genes implicated in VWF biology) on MiSeq (Illumina). Long-read whole genome sequencing (LRS) was performed for the proband on the Oxford Nanopore platform; reads were aligned to GRCh38 using minimap2, variants called (Clair3), and structural variants called (Sniffles2, CuteSV, SVIM).

Results: VWD-Seq NGS data analysis identified no candidates. LRS identified tandem duplication of 3665bps containing exons 9 and 10, predicted to cause an in-frame insertion. The variant validated by orthogonal methods.

Conclusion(s): We here present novel findings resulting in a patient with significant mucocutaneous bleeding, laboratory values all > 50 but a type 2A VWD pattern. We identified a novel VWF duplication of exons 9-10, predicting insertion of 53 amino acids in the VWF propeptide. Propeptide variation is known to cause low VWF protein levels in addition to abnormal multimers. Comprehensive evaluation of the VWF gene for complex variants is warranted to diagnosis VWD, even in patients with high VWF levels.