To examine the presence of genetic anticipation in families with Behçet's syndrome (BS).
A total of 18 families with 40 affected members in two successive generations were evaluated by interviewing them for their ages at the onset of the first symptom of BS and for their ages at the time they fulfilled the diagnostic criteria.
It was noted that the age of onset of the first symptom was lower in the second generation in 14 families (p = 0.01) with a mean (SD) age of 20.57 (7.47) years in the children compared with 33.29 (9.92) years in the parents (t = 7.79, p < 0.0001), whereas the diagnostic criteria were fulfilled at an earlier age in the children in 15 families (p = 0.01) with a mean age of 21.2 (6.74) years in the children compared with 36.4 (9.55) years in the parents (t = 7.41, p < 0.0001).
Genetic anticipation was present in 15 of 18 (84%) of the families with BS in the form of earlier disease onset in the children compared with their parents.