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Controversies in ophthalmology
Predictive DNA testing in ophthalmology: View 1
  1. E Héon
  1. Department of Ophthalmology, University of Toronto, The Hospital for Sick Children and the University Health Network, Toronto, Ontario, M5T 2S8, Canada; eheon@uhnres.utoronto.ca

    https://doi.org/10.1136/bjo.87.5.633-a

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      This family appears to have an early onset autosomal dominant (AD) RP. There is male to male transmission, which excludes X linked RP.1 Although the man‘s father was diagnosed at an older age this may be because the family was unaware of RP at that time. Once the family is aware of the condition and its presenting symptoms they may present earlier, as would appear to be the case with the girl in question. At age 4 years it is unlikely that there would be any abnormality detected on fundus examination.

      RP genes and mutations screening

      There are at least 13 genes that cause ADRP. These are listed in Table 1. An updated listing of retinal dystrophy genes is available on RetNet (http://www.sph.uth.tmc.edu/Retnet/home.htm) and OMIM (http://www3.ncbi.nlm.nih.gov/Omim/searchomim.html).

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      Table 1

      Retinitis pigmentosa, autosomal dominant

      Genetic analysis of RP

      Different approaches can be used to determine the genetic background of a disease depending on the type of samples available. When a family with several affected individuals is available, linkage analysis can be used to include or exclude gene loci of interest. Otherwise, for the more common scenario of sporadic cases, mutational analysis of candidate genes is used.

      Linkage analysis

      If several family members are available for testing and motivated, then a linkage analysis could be performed for the known loci. Definitely unaffected family members are also useful for this analysis. With just three affected members, it may not be possible to be certain which gene is …

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