Summary
Type 3 von Willebrand disease is a rare autosomal disorder characterized by unmeasurable
levels of von Willebrand factor and severe hemorrhagic symptoms. We studied a multiethnic
group of 37 patients, from Italy (n = 14), Iran (n = 10) and India (n = 13) to identify
the molecular defects and to evaluate genetic heterogeneity among these populations.
Twenty-one patients (6 Italians, 9 Iranians and 6 Indians) were fully characterized
at the molecular level. Twenty-four different gene alterations were identified, 20
of which have not been described previously. The majority of the mutations caused
null alleles, 11 being nonsense mutations (Q218*, W222*, R365*, R373*, E644*, Q706*,
S1338*, Q1346*, Y1542*, R1659*, E2129*), 4 small deletions (437delG, 2680delC, 6431delT,
del 8491-8499), 3 possible splice site mutations [IVS9(-1)g→a, IVS29(+10)c→t, IVS40(-1)g
→ c], 3 candidate missense mutations (C275S, C2174G, C2804Y), 2 small insertions (7375insC,
7921insC) and 1 large gene deletion. The latter mutation was associated with the development
of alloantibodies to VWF, but this complication was also found in a patient homozygous
for a nonsense mutation (Q1346*). Due to the ethnic origin of the patients most of
them were the offspring of consanguineous marriages and so were homozygous for the
mutations found (18/21). Our results indicate that molecular defects responsible for
type 3 VWD are scattered throughout the entire VWF gene (from exon 3 to 52), and that
there is no prevalent and common gene defect in the three populations studied by us.
Keywords
von Willebrand factor - type 3 von Willebrand disease - gene analysis - mutation