title: Chromosome abnormality rate among Iranian patients with idiopathic mental retardation from consanguineous marriages.
abstract: BACKGROUND
  Mental retardation (MR) has heterogeneous aetiology mostly with genetic causes. Chromosomal aberrations are one of the most common causes of MR. Reports on chromosome abnormality rate among consanguineous families are sparse. In order to identify the chromosome abnormality rate in idiopathic mental retardation from consanguineous marriages, a total of 322 Iranian families with positive family history for MR were investigated in the Genetics Research Center.
  
  
  METHODS
  In the majority of families (92%) at least two sibs were affected with MR and none had specific chromosomal syndromes such as Down syndrome. Standard cytogenetic techniques using high resolution GTG banding were carried out on all the patients.
  
  
  RESULTS
  The overall chromosome abnormality rate contributing to mental retardation was 1.24% (4 cases), which comprised 46,XY,der(18)t(4;18)(q31.1;q23)mat; 45,XY,-21,-22,+der(22)t(21;22)(q21.1;q13.33)mat; 46,XY,rec(2)dup(2p)inv(2)(p25.1q37.3)pat, and 46,XY,der(11)t(10;11)(q25.2;q25)pat.
  
  
  CONCLUSIONS
  Although the most likely genetic cause of mental retardation in patients with consanguineous parents is autosomal recessive, the fact that 1.24% of our patients had chromosomal abnormalities emphasizes the importance of cytogenetic investigation as the first laboratory genetic tests for all MR patients. To our knowledge, this is the first report on the rate of chromosome abnormality among patients with idiopathic mental retardation from consanguineous marriages.
authors.affiliation: Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.
authors.forename: Farkhondeh
authors.initials: F
authors.lastname: Behjati
authors.forename: Saghar
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authors.lastname: Ghasemi Firouzabadi
authors.forename: Kimia
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authors.lastname: Kahrizi
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authors.lastname: Bagherizadeh
authors.forename: Javad
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authors.lastname: Ansari
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authors.lastname: Mojtahedi
authors.forename: Hossein
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authors.lastname: Darvish
authors.forename: Gholamreza
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authors.lastname: Bahrami Monajemi
authors.forename: S Sedigheh
authors.initials: SS
authors.lastname: Abedini
authors.forename: Payman
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authors.lastname: Jamali
authors.forename: Faezeh
authors.initials: F
authors.lastname: Mojahedi
authors.forename: Azita
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authors.lastname: Zadeh-Vakili
authors.forename: Hossein
authors.initials: H
authors.lastname: Najmabadi