Turner White CommunicationsAbout TWCSubscribeContact TWCHomeSearch
Hospital PhysicianJCOMSMPBRMsCart
Current Contents
Past Issue Archives
Interactive:
Self-Assessment Questions
Review of
Clinical Signs
Clinical Review
Quiz
Pediatric Rounds
Resident Grand Rounds
Article Archives
Case Reports
Clinical Practice
Exams
Pediatric Rounds
Resident Grand Rounds
Review of
Clinical Signs

Guide to Reading
Hospital Physician
Editorial Board
Information for Authors

Reprints, Permissions, & Copyright
Site Map
Self-Assessment Questions

Neurology


Answer 6
  1. Trinucleotide repeat expansion. Huntington’s disease, like many other neurodegenerative disorders, is characterized by a trinucleotide repeat expansion. The cytosine-adnenine-guanine repeat expansion (exon 1) is translated, producing an expanded polyglutamine tract. The size of the expansion correlates with the age of onset and, as some have suggested, the rate of progression.11 This relationship does not provide sufficiently precise information to have prognostic relevance.12 The trinucleotide repeat expansion is unstable and tends to expand with generational transmission. This instability provides a mechanism for anticipation, resulting in an earlier age of onset in succeeding generations. The largest expansions are seen with paternal transmission, thus accounting for the association of juvenile-onset Huntington’s disease with an affected father.13

    REFERENCES
    11. Kremer B, Goldberg P, Andrew SE, et al. A worldwide study of the Huntington’s disease mutation. The sensitivity and specificity of measuring CAG repeats. N Engl J Med 1994;330:1401-6.

    12. Lucotte G, Turpin JC, Riess O, et al. Confidence intervals for predicted age of onset, given the size of (CAG)n repeat, in Huntington’s disease. Hum Genet 1995;95:231-2.

    13. Ranen NG, Stine OC, Abbott MH, et al. Anticipation and instability of IT-15 (CAG)n repeats in parent-offspring pairs with Huntington disease. Am J Hum Genet 1995;57:593-602.

Click here to return to the questions

 

Hospital Physician     JCOM     Seminars in Medical Practice
Hospital Physician Board Review Manuals
About TWC    Subscribe    Contact TWC    Home    Search   Site Map

Copyright © 2009, Turner White Communications
Updated 1/04/08 • kkj