Isolated 6q Terminal Deletions: an Emerging New Syndrome

Deletions of the distal part of the 6q chromosome have not been associated with a clearly distinctive and recognizable phenotype. In order to determine if a "6q terminal deletion syndrome" could be delineated, we compared the phenotype of two new cases with those patients reported in literature presenting with a similar deletion. Cases with more complex karyotypes were excluded. The deletion in our patients was accurately analyzed by loss of heterozygosity (LOH) and fluorescence in situ hybridization (FISH) with a panel of probes located around the putative breakpoint. Interestingly, the breakpoints were located in 6q26 in both our patients, distally to clone RP11-150P20 and proximally to clone RP11-152P19, with a deletion size of approximately 8 Mb. The breakpoints fall within the fragile site FRA6E. From a careful evaluation of the selected patients, a common phenotype emerged, including psychomotor retardation, hypotonia, seizures, short neck, and typical facial anomalies, along with nonspecific anomalies. While these features are shared by other chromosome syndromes and are not sufficient on their own for a clinical diagnosis, when considered together, the pattern can allow the identification of the "6q terminal deletion syndrome." Moreover, the potential role of FRA6E in generating these deletions is suggested.