BILINEAL TRANSMISSION IN TOURETTES-SYNDROME FAMILIES

We assessed the frequency of bilineal (from maternal and paternal side s) transmission of Tourette's syndrome (TS) in two groups of pedigrees : (1) 39 high-density families in which five or more relatives were re ported to have TS, and (2) the families of 39 consecutively ascertaine d probands referred for evaluation of TS. We used two designations for the TS phenotype (ties, ties or obsessive-compulsive behavior [OCB]), and we attempted to verify bilineal transmission with direct examinat ions. For the high-density pedigrees, bilineal transmission was eviden t in 33% (considering ties) and 41% (considering ties or OCB) of famil ies, which was confirmed by examination in 77% of the kindreds. For th e consecutive pedigrees, bilineal transmission was seen in 15% (ties) and 26% (ties or OCB) of families, which was verified by examination i n 66% of the kindreds. Both parents of the proband were affected (ties or OCB) in 38% of the high-density pedigrees and 10% of the consecuti ve pedigrees. For the high-density families only, the frequency of bil ineal transmission appeared to be related to the proband's severity of TS, and for both pedigree groups, the frequency of both parents being affected was higher in families in which the proband's symptoms were most severe. Our findings support the contention that bilineal transmi ssion and homozygosity are common in TS. These genetic phenomena might play a role in determining severity of illness and may explain curren t difficulties in localizing the gene defect by linkage analysis.