Huntington disease (HD), an autosomal dominant disorder with variable age of onset, has in the past posed a problem in linkage analysis. The available methodology was inefficient in dealing with such disorders where precise genotypic classification of at-risk individuals is impossible. Using the standard z-score method of Morton, for example, only older individuals over, say, the 90th percentile for risk could be scored. Thus, the amount of information on a particular family was significantly decreased. One had to select families with two or three living affected generations. Since this type of HD family is difficult to find, due to the disease's variable age of onset, the amount of useful data was severely limited. One could, of course, simply wait for at-risk family members to become affected or pass into the low-risk age years; this approach is usually impractical due to the time span involved. Recent developments in methodology and computer programs circumvent the difficulty in working with variable age of onset disorders. Information on individuals at risk can be incorporated into the analysis, substantially increasing the amount of information on a family. The method described, although used specifically in the analysis of linkage with HD, can serve as a model for other variable age of onset or nonpenetrant disorders.
ASJC Scopus subject areas
- Molecular Biology