title: [Fragile X syndrome is still unrecognized: efficacy of molecular diagnosis in mentally retarded probands].
abstract: BACKGROUND
  The fragile X mental retardation syndrome is the most common cause of inherited mental retardation. Identification of the unstable mutation responsible for the disease has allowed the design of a fully reliable molecular test for the diagnosis of the disease and for genetic counselling (identification of clinically normal carriers and prenatal diagnosis). We started in July 1991 to search for the mutation in mentally retarded probands, with no known cause for their phenotype. We present the results of a 42-month experience.
  
  
  METHODS
  One thousand and one hundred fourty-nine probands were analysed. In case of a positive diagnosis, an extension of the molecular study to relatives was proposed. DNA samples were studied by Southern blot following EcoRI or EcoRI + EagI digestion. Clinical data were collected from referring clinicians.
  
  
  RESULTS
  Seventy-three carriers of a full mutation were identified, belonging to 52 families. The mean age of the fragile X probands was 16 +/- 14 years, which is very surprising for a disease that causes significant manifestations by the age of 2 to 3 years. This indicates an insufficient knowledge about this disease in France. Most of the demands for the test were from clinical geneticists. This diagnosis is of major importance for genetic counselling, as illustrated by the following study of 108 women at risk in these families.
  
  
  CONCLUSIONS
  The importance of an early diagnosis followed by an extended family study, for carrier screening and prevention of this severe disease, justifies molecular testing on any child with mental retardation or significant language delay of unknown cause, in the absence of clinical signs formally excluding a fragile X diagnosis.
authors.affiliation: Laboratoire de génétique moléculaire humaine, faculté de médecine, Strasbourg, France.
authors.forename: M
authors.initials: M
authors.lastname: Cossée
authors.forename: C
authors.initials: C
authors.lastname: Moutou
authors.forename: V
authors.initials: V
authors.lastname: Biancalana
authors.forename: J C
authors.initials: JC
authors.lastname: Bouix
authors.forename: G
authors.initials: G
authors.lastname: Plessis
authors.forename: B
authors.initials: B
authors.lastname: Delobel
authors.forename: M F
authors.initials: MF
authors.lastname: Croquette
authors.forename: S
authors.initials: S
authors.lastname: Gilgenkrantz
authors.forename: J C
authors.initials: JC
authors.lastname: Lambert
authors.forename: G
authors.initials: G
authors.lastname: Malpuech
authors.forename: C
authors.initials: C
authors.lastname: Stoll
authors.forename: J L
authors.initials: JL
authors.lastname: Lanoe
authors.forename: M
authors.initials: M
authors.lastname: Pechevis
authors.forename: J L
authors.initials: JL
authors.lastname: Mandel
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D005600:Fragile X Syndrome / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D008967:Molecular Biology; D010375:Pedigree