title: A Family with Mental Retardation, Epilepsy and Cerebellar Hypoplasia Showing Linkage to Chromosome 20p11.21-q11.23.
abstract: BACKGROUND
  Cerebellar hypoplasia (CH) is a rare malformation caused by various etiologies, usually manifesting clinically as nonprogressive cerebellar ataxia with or without mental retardation. The molecular pathogenesis of the autosomal recessive cerebellar ataxias has a wide range of mechanisms. Differential diagnosis and categorization of the recessive cerebellar ataxias, however, need more specific, biochemical and genetic investigation.
  
  
  METHODS
  This study applied whole-genome linkage analysis to study a family with nonprogressive cerebellar ataxia and additional mental retardation, epilepsy, and facial dysmorphic features. Genotyping and linkage analysis was done using the GeneChip Mapping 250K NspI Array (Affymetrix Inc., Santa Clara, Calif., USA) for genome-wide linkage analysis of the genotyping data from the affected children and their parents.
  
  
  RESULTS
  Allegro software version 1.2 was used for multipoint linkage analysis. We assumed an autosomal recessive inheritance pattern and assigned a penetrance of 0.999. Single-nucleotide polymorphism allele frequencies were estimated from the Affymetrix data of the Caucasian family studied. Using these parameters, a theoretical maximum logarithm of the odds score of 2.69 was identified at chromosome 20p11.21-q11.23.
  
  
  CONCLUSIONS
  This chromosomal locus is unprecedented in autosomal recessive and nonprogressive ataxia disorder. Further investigation might reveal a new causative gene generating the CH phenotype.
authors.affiliation: Department of Neurosurgery, Cumhuriyet University School of Medicine, Sivas, Kayseri, Turkey.
authors.forename: Fatih
authors.initials: F
authors.lastname: Bayrakli
authors.affiliation: Department of Child Neurology, Erciyes University School of Medicine, Kayseri, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Canpolat
authors.affiliation: Department of Child Neurology, Erciyes University School of Medicine, Kayseri, Turkey.
authors.forename: Huseyin
authors.initials: H
authors.lastname: Per
authors.affiliation: Department of Child Neurology, Erciyes University School of Medicine, Kayseri, Turkey.
authors.forename: Hakan
authors.initials: H
authors.lastname: Gumus
authors.affiliation: Department of Child Neurology, Erciyes University School of Medicine, Kayseri, Turkey.
authors.forename: Sefer
authors.initials: S
authors.lastname: Kumandas
authors.affiliation: Neurogenetic Research Laboratory at, Cumhuriyet University School of Medicine, Sivas, Kayseri, Turkey.
authors.forename: Ugur
authors.initials: U
authors.lastname: Kartal
authors.affiliation: Department of Neurology, Cumhuriyet University School of Medicine, Sivas, Kayseri, Turkey.
authors.forename: Hatice
authors.initials: H
authors.lastname: Balaban
keywords: Cerebellar hypoplasia; Logarithm of the odds score; Mental retardation; Parametric linkage analysis