DELETION IN THE FMR1 GENE IN A FRAGILE-X MALE

The pathogenesis of Fragile-X syndrome is a consequence of absence of the FMR1 gene product associated with expansion of the CGG repeat and abnormal methylation of this and a CpG island 250 bp proximal to the C GG repeat located at exon 1 in the FMR1 gene. While this is usually th e case, some suspected Fragile-X syndrome patients have been described with a mutation other than CGG expansion. We describe here an affecte d Fragile-X male, who was found to be mosaic of a full mutation of the CGG expansion and a deletion in the FMR1 gene. The patient's phenotyp e is probably mainly due to the effect of the full mutation of the rep eat sequence. Thus, the influence of the deletion is difficult to eval uate. (C) 1996 Wiley-Liss, Inc.