Linkage analysis in families diagnosed with type 1 von Willebrand disease in the European study, molecular and clinical markers for the diagnosis and management of type 1 VWD

• Background: von Willebrand disease (VWD) type 1 is a congenital bleeding disorder caused by genetic defects in the von Willebrand factor (VWF) gene and characterized by a reduction of structurally normal VWF. The diagnosis of type 1 VWD is difficult because of clinical and laboratory variability. Furthermore, inconsistency of linkage between type 1 VWD and the VWF locus has been reported. Objectives: To estimate the proportion of type 1 VWD that is linked to the VWF gene. Patients and methods: Type 1 VWD families and healthy control individuals were recruited. An extensive questionnaire on bleeding symptoms was completed and phenotypic tests were performed. Linkage between VWF gene haplotypes and the diagnosis of type 1 VWD, the plasma levels of VWF and the severity of bleeding symptoms was analyzed. Results: Segregation analysis in 143 families diagnosed with type 1 VWD fitted a model of autosomal dominant inheritance. Linkage analysis under heterogeneity resulted in a summed lod score of 23.2 with an estimated proportion of linkage of 0.70. After exclusion of families with abnormal multimer patterns the linkage proportion was 0.46. LOD scores and linkage proportions were higher in families with more severe phenotypes and with phenotypes suggestive of qualitative VWF defects. About 40% of the total variation of VWF antigen could be attributed to the VWF gene. Conclusions: We conclude that the diagnosis of type 1 VWD is linked to the VWF gene in about 70% of families, however after exclusion of qualitative defects this is about 50%.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Kardiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Cardiac and Cardiovascular Systems (hsv//eng)

Keyword

von Willebrand disease

type 1

linkage analysis

co-segregation

bleeding score

blood group

Publication and Content Type

art (subject category)

ref (subject category)