Fragile X syndrome without CCG amplification has an FMR1 deletion

Nat Genet. 1992 Aug;1(5):341-4. doi: 10.1038/ng0892-341.


We describe a patient with typical clinical features of the fragile X syndrome, but without cytogenetic expression of the fragile X or an amplified CCG trinucleotide repeat fragment. The patient has a previously uncharacterized submicroscopic deletion encompassing the CCG repeat, the entire FMR1 gene and about 2.5 megabases of flanking sequences. This finding confirms that the fragile X phenotype can exist, without amplification of the CCG repeat or cytogenetic expression of the fragile X, and that fragile X syndrome is a genetically homogeneous disorder involving FMR1. We also found random X-inactivation in the mother of the patient who was shown to be a carrier of this deletion.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Base Sequence
  • Cells, Cultured
  • Chromosome Banding
  • Chromosome Mapping
  • Female
  • Fragile X Mental Retardation Protein
  • Fragile X Syndrome / genetics*
  • Gene Deletion*
  • Humans
  • Karyotyping
  • Lymphocytes / physiology
  • Male
  • Nerve Tissue Proteins / genetics*
  • Pedigree
  • RNA-Binding Proteins*
  • Repetitive Sequences, Nucleic Acid
  • X Chromosome*


  • FMR1 protein, human
  • Nerve Tissue Proteins
  • RNA-Binding Proteins
  • Fragile X Mental Retardation Protein