Disease: Von-willebrand Disorder Type 2M

Patient1: 13 YO male

Patient2: 16 YO female

Note they are siblings

Variant: VWF NM_000552.5: c.5192C>T p.(Ser1731Leu), heterozygous variant, in A3 domain in exon 30

Phenotype patient 1: several bleedings after tosillectomy, recurrent epistaxis, decreased VWF:CB ratio, decreased VWF:CB/VWF:Ag ratio

Phenotype patient 2: menorrhagia, intermittent gum bleeding, easy bruising, decreased VWF:CB ratio, decreased VWF:CB/VWF:Ag ratio

For both patients: VWF:CB ratio corresponds to collagen type 1, multimer analysis was normal, VWF:Ag, VWF:Ac, and factor VIII activity was normal.

Family: Not listed

Present in dbSNP (rs764077750)

Present in gnomAD, rare MAF (ALL: 0.0012%)

Predictions:

SIFT- predicted deleterious (Score 0.01, median 3.34)

MutationTaster- Predicted disease causing (probability score 1)

PolyPhen2- Predicted probably damaging (Score 0.983)

CADD score- 26.5

Authors mention similar AA substitutions at the p.1731 position which leads to reduced binding of VWF to collagen in other patients.

Authors also cite a functional human cell experiment in COS7 cell line which resulted in functional VWF defect.

Authors conclude this novel variant as likely pathogenic.