RT Journal Article
SR Electronic
T1 Myotonic dystrophy: the correlation of (CTG) repeat length in leucocytes with age at onset is significant only for patients with small expansions
JF Journal of Medical Genetics
JO J Med Genet
FD BMJ Publishing Group Ltd
SP 59
OP 61
DO 10.1136/jmg.36.1.59
VO 36
IS 1
A1 Marion G Hamshere
A1 Helen Harley
A1 Peter Harper
A1 J David Brook
A1 John F Y Brookfield
YR 1999
UL http://jmg.bmj.com/content/36/1/59.abstract
AB Myotonic dystrophy (DM) was the first of a group of diseases to be identified for which the genetic basis is the expansion of a triplet repeat. Myotonic dystrophy also exhibits anticipation, in which the disease worsens through successive generations. These two features have led many groups to analyse whether a significant negative correlation between triplet repeat length and severity of disease exists. However, the recent molecular finding that two distinct subsets of classically affected DM patients exist, those who export expansion derived DMPK RNA and those who do not, led us to question whether combining data from these two sets of patients is statistically valid. We found that although patients with small expansions showed a significant correlation between age at onset and triplet repeat length, those with larger expansions did not. The theoretical triplet repeat size, which separated the two groups, was also deduced.