title: Genetic heterogeneity of FG syndrome: a fourth locus (FGS4) maps to Xp11.4-p11.3 in an Italian family.
abstract: FG syndrome (FGS, MIM 305450) is a rare X-linked recessive disorder comprising mental retardation and multiple malformations. Various families have been described to date, increasing our knowledge of the phenotype variability and making the clinical diagnosis complex, especially in sporadic patients. The first locus for FG syndrome (FGS1) was linked to chromosome region Xq12-q21.31, but other families have been excluded from this locus. The genetic heterogeneity of FG syndrome has been confirmed by analysis of an X chromosome inversion [inv(X)(q11q28)] in an affected boy and in his mentally retarded maternal uncle, suggesting that an additional locus for FG syndrome (FGS2, MIM 300321) is located at either Xq11 or Xq28. Recently, a third locus (FGS3) has been mapped to Xp22.3. We have identified and clinically characterized an Italian FG family, including 31 members with three affected males in two generations and two obligate carriers. We have excluded linkage to known FGS loci, whereas an extensive study of the whole X chromosome has yielded a maximum LOD score (Z(max)) of 2.66 (recombination fraction=0) for markers between DXS8113 and sWXD805. This new locus for FG syndrome corresponds to a region of approximately 4.6 Mb on the X chromosome.
authors.affiliation: Dipartimento di Patologia Generale, Facoltà di Medicina e Chirurgia, Seconda Università degli Studi di Napoli, Via Luigi De Crecchio 7, 80138 Naples, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Piluso
authors.forename: Massimo
authors.initials: M
authors.lastname: Carella
authors.forename: Michele
authors.initials: M
authors.lastname: D'Avanzo
authors.forename: Raffaele
authors.initials: R
authors.lastname: Santinelli
authors.forename: Elena Maria
authors.initials: EM
authors.lastname: Carrano
authors.forename: Angelo
authors.initials: A
authors.lastname: D'Avanzo
authors.forename: Adamo Pio
authors.initials: AP
authors.lastname: D'Adamo
authors.forename: Paolo
authors.initials: P
authors.lastname: Gasparini
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Nigro
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D001526:Behavioral Symptoms / Q000235:genetics; D002675:Child, Preschool; D002874:Chromosome Mapping; D041321:Chromosomes, Human, X; D005145:Face / Q000002:abnormalities*; D005260:Female; D018740:Genetic Heterogeneity; D008040:Genetic Linkage; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D007558:Italy; D008126:Lod Score; D008297:Male; D018895:Microsatellite Repeats; D009123:Muscle Hypotonia / Q000235:genetics; D010375:Pedigree; D013577:Syndrome