title: Outcome of ABCA4 disease-associated alleles in autosomal recessive retinal dystrophies: retrospective analysis in 420 Spanish families.
abstract: OBJECTIVE
  To provide a comprehensive overview of all detected mutations in the ABCA4 gene in Spanish families with autosomal recessive retinal disorders, including Stargardt's disease (arSTGD), cone-rod dystrophy (arCRD), and retinitis pigmentosa (arRP), and to assess genotype-phenotype correlation and disease progression in 10 years by considering the type of variants and age at onset.
  
  
  METHODS
  Case series.
  
  
  METHODS
  A total of 420 unrelated Spanish families: 259 arSTGD, 86 arCRD, and 75 arRP.
  
  
  METHODS
  Spanish families were analyzed through a combination of ABCR400 genotyping microarray, denaturing high-performance liquid chromatography, and high-resolution melting scanning. Direct sequencing was used as a confirmation technique for the identified variants. Screening by multiple ligation probe analysis was used to detect possible large deletions or insertions in the ABCA4 gene. Selected families were analyzed further by next generation sequencing.
  
  
  METHODS
  DNA sequence variants, mutation detection rates, haplotypes, age at onset, central or peripheral vision loss, and night blindness.
  
  
  RESULTS
  Overall, we detected 70.5% and 36.6% of all expected ABCA4 mutations in arSTGD and arCRD patient cohorts, respectively. In the fraction of the cohort where the ABCA4 gene was sequenced completely, the detection rates reached 73.6% for arSTGD and 66.7% for arCRD. However, the frequency of possibly pathogenic ABCA4 alleles in arRP families was only slightly higher than that in the general population. Moreover, in some families, mutations in other known arRP genes segregated with the disease phenotype.
  
  
  CONCLUSIONS
  An increasing understanding of causal ABCA4 alleles in arSTGD and arCRD facilitates disease diagnosis and prognosis and also is paramount in selecting patients for emerging clinical trials of therapeutic interventions. Because ABCA4-associated diseases are evolving retinal dystrophies, assessment of age at onset, accurate clinical diagnosis, and genetic testing are crucial. We suggest that ABCA4 mutations may be associated with a retinitis pigmentosa-like phenotype often as a consequence of severe (null) mutations, in cases of long-term, advanced disease, or both. Patients with classical arRP phenotypes, especially from the onset of the disease, should be screened first for mutations in known arRP genes and not ABCA4.
authors.affiliation: Department of Genetics, Instituto de Investigacion Sanitaria-Fundacion Jimenez Diaz (IIS-FJD), Madrid, Spain; Centro de Investigacion Biomedica en Red (CIBER) de Enfermedades Raras, ISCIII, Madrid, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Riveiro-Alvarez
authors.forename: Miguel-Angel
authors.initials: MA
authors.lastname: Lopez-Martinez
authors.forename: Jana
authors.initials: J
authors.lastname: Zernant
authors.forename: Jana
authors.initials: J
authors.lastname: Aguirre-Lamban
authors.forename: Diego
authors.initials: D
authors.lastname: Cantalapiedra
authors.forename: Almudena
authors.initials: A
authors.lastname: Avila-Fernandez
authors.forename: Ascension
authors.initials: A
authors.lastname: Gimenez
authors.forename: Maria-Isabel
authors.initials: MI
authors.lastname: Lopez-Molina
authors.forename: Blanca
authors.initials: B
authors.lastname: Garcia-Sandoval
authors.forename: Fiona
authors.initials: F
authors.lastname: Blanco-Kelly
authors.forename: Marta
authors.initials: M
authors.lastname: Corton
authors.forename: Sorina
authors.initials: S
authors.lastname: Tatu
authors.forename: Patricia
authors.initials: P
authors.lastname: Fernandez-San Jose
authors.forename: Maria-Jose
authors.initials: MJ
authors.lastname: Trujillo-Tiebas
authors.forename: Carmen
authors.initials: C
authors.lastname: Ramos
authors.forename: Rando
authors.initials: R
authors.lastname: Allikmets
authors.forename: Carmen
authors.initials: C
authors.lastname: Ayuso
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000483:Alleles; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D004596:Electroretinography; D005451:Fluorescein Angiography; D056726:Genetic Association Studies; D060005:Genotyping Techniques; D006801:Humans; D008268:Macular Degeneration / Q000175:diagnosis / Q000235:genetics; D008875:Middle Aged; D060885:Multiplex Polymerase Chain Reaction; D009154:Mutation; D012174:Retinitis Pigmentosa / Q000175:diagnosis / Q000235:genetics*; D012189:Retrospective Studies; D013030:Spain; D000080362:Stargardt Disease; D055815:Young Adult
chemical_list: C056475:ABCA4 protein, human; D018528:ATP-Binding Cassette Transporters