title: [Early diagnosis of retinoblastoma: usefulness of searching for RB1 gene mutations].
abstract: BACKGROUND
  Retinoblastoma, the intraocular malignancy most common in children,occurs in both familial and sporadic (bilateral or unilateral). Hereditary predisposition is caused by a germ-line mutation while non-hereditary is due to two somatic mutations in a retinal cell. This work was carried out in order to analyse genetically, the high number of families with some affected member and to go deep into the molecular mechanisms responsible of this pathology.
  
  
  METHODS
  59 families with one or more affected members were analysed. Cytogenetics and with polymorphic markers studies were carried out and a search for mutations was performed in DNA from white cells and from available tumoral tissue.
  
  
  RESULTS
  In four of the 5 familial cases, the responsible mutation was established,the same as in 9 of the 13 bilateral sporadic. In the 7% of the unilateral sporadic cases, mutation was found in leucocytary DNA. Lost of heterozygosity as a second mutational event was mainly due to mitotic recombination.
  
  
  CONCLUSIONS
  Among the mutations of our series, a higher frequency of punctual mutations,responsible of the first mutational event, was observed at constitutional level. Lost of heterozygosity was the mechanism observed in the majority of the tumours.
authors.affiliation: Departamento de Genética. Facultad de Ciencias Biológicas. Universitat de Valencia. carmen.najera@uv.es
authors.forename: C
authors.initials: C
authors.lastname: Nájera
authors.forename: F
authors.initials: F
authors.lastname: Sánchez
authors.forename: E
authors.initials: E
authors.lastname: Mateu
authors.forename: F
authors.initials: F
authors.lastname: Prieto
authors.forename: M
authors.initials: M
authors.lastname: Beneyto
mesh_terms: D004252:DNA Mutational Analysis; D005260:Female; D016161:Genes, Retinoblastoma / Q000235:genetics*; D006801:Humans; D019656:Loss of Heterozygosity; D008297:Male; D009154:Mutation; D010375:Pedigree; D012175:Retinoblastoma / Q000175:diagnosis / Q000235:genetics*