Disease: Von-Willebrand Disorder

Patient 2 Variant(s):

VWF NM_000552.5: c.4135C>T p.(Arg1379Cys) Exon 28 VWF NM_000552.5: c.4130C>T p.(Ala1377Val) Exon 28 VWF NM_000552.5: c.3797C>T p.(Pro1266Leu) Exon 28 VWF NM_000552.5: c.3835G>A p.(Val1279Ile) Exon 28

Note: Pro1266Leu and Val1279Ile are in trans with Ala1377Val and Arg1379Cys

Note2: MAF of Ala1377Val is present in Exome Variant Server (<0.01) and 1000 Genomes database (<0.02), designated as rare variant, typically found in indiv with African ethnicity

Family: Relatives molecular analysis showed Arg1379 and Ala1377Val variants mentioned above were in cis

Patient 2 Phenotype: Mild bleeding symptom Nearly normal VWF:Ag value, reduced VWF:RCo value slight loss of HMWM with smear decreased/slightly decreased proteolysis Slightly reduced RIPA VWFpp/VWF:Ag ratio shows increased VWF clearance VWF platelet levels reduced reduced rBpIba binding in VWF plasma VWF:GPIbM values slightly increased

Note: Treated with desmopressin in case of minor surgeries or delivery

Note 2: Slightly decreased RIPA may be explained by presence of 2B New York Variant (Pro1266Leu) that mitigates RIPA assay in 2M phenotype.

In silico analysis available:

I-Mutant 3.0 states decrease in A1 domain stability for both mutations (Ala1377Val = -0.91, Arg1379Cys = -1.36)

PYMOL predicts Ala1377Val does not alter formation of hydrogen bonds with Arg1374 residue and water. Predicts substitution of ARG 1379 with a cysteine results in the loss of hydrogen bonds with Lys1407 and Lys1408, predicted change in secondary structure of A1 domain

Ala1377Val was previously reported in 3 other patients Publications:

Millar CM, Riddel AF, Mellors G, Yee TT. The spectrum of VWD type 2 phenotypes associated with A1 domain mutations posters. J Thromb Haemost 2009; 7: 531–2.

Logsdon BA, Dai JY, Auer PL et al. A variational Bayes discrete mixture test for rare variant association. Genet Epidemiol 2014; 38: 21–30.

Final note: Authors suggest patients' 2M phenotype is due to the presence of Ala1377Val and Arg1379Cys together to create synergistic effect. Though difficult to discern with this specific patient having two other variants in addition to the two mentioned above.