FRAGILE-X-SYNDROME AND DELETIONS IN FMR1 - NEW CASE AND REVIEW OF THELITERATURE

The fragile X syndrome phenotype of mental retardation is almost alway s caused by abnormal CGG trinucleotide amplification within the FMR1 g ene, Occasionally fragile X syndrome results from point mutations or d eletions within or around the FMR1 locus. We have identified a mentall y retarded African American male with typical fragile X phenotype and a 300-400 base pair intragenic deletion near the CGG repeat segment, p resent in his peripheral blood lymphocytes with no apparent mosaicism. His mother, who is not retarded, has a full FMR1 CGG expansion mutati on with 700-900 repeats, A review of 23 published cases with FMR1 gene deletions shows full FMR1 mutation in the mother of only 1 other prop ositus, a male with FMR1 full mutation/premutation/deletion mosaicism of his cultured skin fibroblasts and peripheral blood lymphocytes. The various deletions within FMR1 and their clinical significance are rev iewed. (C) 1997 Wiley-Liss, Inc.