Onset and repeat length in CAG repeat disorders
Data compiled from published reports were used to calculate mean age at neurologic onset (as in Fig. 1) associated with different CAG repeat lengths in the disease alleles of 92 SCA2 cases (diamonds), 201 SCA1 cases (inverted triangles) (78–81), 1226 HD cases (circles) (10,13,21,23–26,28–31,34,36,37,42, 75–77), 149 DRPLA cases (squares) (58,82–84) and 332 MJD/SCA3 cases (triangles) (64,68,69,85–87). Each panel also shows the curve-fit (line; r2 = .867 (SCA2); .952 (SCA1); .970 (HD); .943 (DRPLA); .968 (MJD/SCA3) for the mean age at onset with an exponential model similar to that used in Fig. 1. Filled symbols in each panel represent individuals homozygous for the corresponding disease allele, with age at onset plotted against the number of CAG repeats in larger of the two disease alleles (61,81,88–92).