Takayasu's disease in twin sisters. Possible genetic factors

Takayasu's disease is well-known for its characteristic clinical features and its elusive etiology. Recently, we encountered twin Japanese sisters, both of whom were diagnosed as having Takayasu's disease. The parents, two sisters, and one brother are healthy. Family history revealed the parents are first cousins. Analyses of serveral blood types and HLA typing were performed on all members of the family, and it was confirmed that these twins are monozygotic. Moreover, HLA typing analyses revealed that one haplotype found in the father was passed only to these twins. The history of consanguinity of the parents, the occurrence in twins, and the results of HLA typing suggest a genetic factor in the etiology of Takayasu's disease.