We report on 3 kindred patients with terminal 11q monosomy and distal 22q trisomy involving the SHANK3 gene, resulting from a subtle familial translocation t(11;22)(q24.2;q13.33). The patients presented with the characteristic symptoms of Jacobsen syndrome (JBS), including: mental retardation, short stature, and craniofacial dysmorphism in all 3 cases; cardiac defects in 2 cases; and thrombocytopenia, brain abnormality, eye coloboma, recurrent infections, cryptorchidism and toe anomalies in single cases. The oldest patient also had Hashimoto disease and diabetes mellitus type 2. So far, these 2 conditions have not been reported in adult patients with JBS. Features typical for distal 22q trisomy in our patients include muscular hypotonia and prenatal failure to thrive, seen in 2 and 1 cases, respectively. We also present a family member with 11q24.2-qter trisomy and 22q13.33-qter monosomy, whose clinical phenotype is partially overlapping with several dysmorphic features of JBS. In addition, multiple pregnancy losses and infantile deaths occurred in this family, suggesting that these chromosomal imbalances may produce a lethal phenotype. FISH with a panel of BAC probes determined the accurate sizes of the deletion 11q (9.9 Mb) and trisomy 22q (0.8 Mb). To date, only 5 cases of submicroscopic 22q13.3-qter trisomy have been reported. A detailed clinical description of our patients, along with a precise cytogenetic designation of chromosomal breakpoints, allow further refinement of genotype-phenotype correlation for distal imbalances in 11q and 22q.