Pedigree and laboratory data of a family diagnosed with von Willebrand disease. Affected patients are represented by black symbols; unaffected persons, by half-filled symbols; squares, males; and circles, females. The laboratory test results are listed as follows: VWF:Ag (U/dL), VWF:CB (U/dL), platelet (plt) VWF:Ag (U/10¹¹ plts), and FVIII:C (U/dL); nd indicates not determined. Affected patients (black symbols) were found to have a homozygous N528S VWF mutation, whereas unaffected (half-filled symbols) were heterozygous for the mutation. Affected, N528S VWF homozygous patients had low VWF:Ag with substantially reduced VWF:CB and platelet VWF:Ag.