Deletion of 8.5 Mb, including the FMR1 gene, in a male with the fragile X syndrome phenotype and overgrowth

A four-year-old boy with severe psychomotor retardation, facial appearance consistent with the fragile X syndrome, hypotonia, and overgrowth was found to have a deletion including the fragile X gene (FMR1). The breakpoints of the deletion were established between CDR1 and sWXD2905 (approximately 200 kb apart) at Xq27.1 (centromeric) and between DXS8318 (612-1078L) and DXS7 847 (576-291L) (approximately 250 kb apart) at Xq28, about 500 kb telomeric to the FMR1 gene. The total length of the deletion is approximately 8.5 Mb . The propositus's mother, who was found to be a carrier of the deletion, s howed very mild mental impairment. Except for mental retardation, which is a common finding in all cases reported with similar deletions of chromosome Xq, this patient had generalized overgrowth, exceeding the 97th centile fo r height and weight, Obesity and increased growth parameters have been repo rted in other patients with deletions either overlapping or within a distan ce of 0.5 Mb from the deletion in the present patient. Thus, it is suggeste d that a deletion of the 8-Mb fragment centromeric to the FMR1 gene might h ave an effect on growth. (C) 1999 Wiley-Liss, Inc.