Co-existence of Bernard Soulier syndrome and factor XI deficiency in a family: a unified pathology?

Bernard Soulier syndrome (BSS) is an autosomal recessive disorder of platelet function. Factor XI deficiency leads to a variable bleeding tendency and the defect is also inherited in an autosomal recessive manner. In this paper we describe a case of BSS with severe deficiency of factor XI. The patient had both BSS and factor XI deficiency. The sister and both the parents were heterozygous for BSS and had factor XI deficiency. The brother is normal for both BSS and factor XI levels. Apart from the patient, no other family members had any history of bleeding in spite of having a deficiency of factor XI, which suggests that low level of factor XI in this family was not responsible for bleeding. Curiously, although the index patient inherited both Bernard Soulier syndrome and factor XI deficiency (FXI: C = 1.3%), he had mild bleeding symptoms restricted only to ecchymoses and petechiae. Detailed review of the pedigree showed that all the members who inherited the BSS phenotype, also inherited abnormal factor XI gene. Karyotype of the affected members of the family using standard Giemsa banding technique showed a normal picture. Considering the fact that the genes causing both BSS and factor XI are both on widely different chromosomes, their coinheritance in four members of the family without any unusual translocation suggest a unified pathology probably on the basis of a common transcription factor defect or a common post translational processing defect. This is the first case of coinheritance of BSS and factor XI deficiency reported in the English literature.