We tested the hypothesis that variant repeat interruptions (RIs) within the DMPK CTG repeat tract lead to milder symptoms compared with pure repeats (PRs) in myotonic dystrophy type 1 (DM1).

We evaluated motor, neurocognitive, and behavioral outcomes in a group of 6 participants with DM1 with RI compared with a case-matched sample of 12 participants with DM1 with PR and a case-matched sample of 12 unaffected healthy comparison participants (UA).

In every measure, the RI participants were intermediate between UA and PR participants. For muscle strength, the RI group was significantly less impaired than the PR group. For measures of Full Scale IQ, depression, and sleepiness, all 3 groups were significantly different from each other with UA > RI > PR in order of impairment. The RI group was different from unaffected, but not significantly different from PR (UA > RI = PR) in apathy and working memory. Finally, in finger tapping and processing speed, RI did not differ from UA comparisons, but PR had significantly lower scores than the UA comparisons (UA = RI > PR).

Our results support the notion that patients affected by DM1 with RI demonstrate a milder phenotype with the same pattern of deficits as those with PR indicating a similar disease process.

我们测试了这样的假设，即与 1 型强直性肌营养不良症 (DM1) 中的纯重复 (PR) 相比， DMPK CTG 重复区中的变异重复中断 (RI) 导致症状较轻。

我们评估了一组 6 名患有 RI 的 DM1 参与者的运动、神经认知和行为结果，并与 12 名患有 PR 的 DM1 参与者的病例匹配样本和 12 名未受影响的健康比较参与者 (UA) 的病例匹配样本进行了比较。

在每一项测量中，RI 参与者都介于 UA 和 PR 参与者之间。对于肌肉力量，RI 组的受损程度明显低于 PR 组。对于全量表智商、抑郁和嗜睡的测量，所有 3 组均存在显着差异，即 UA > RI > PR，按损伤顺序排列。RI 组在冷漠和工作记忆方面与未受影响的组不同，但与 PR (UA > RI = PR) 没有显着差异。最后，在手指敲击和处理速度方面，RI 与 UA 比较没有差异，但 PR 的得分明显低于 UA 比较（UA = RI > PR）。

我们的结果支持这样一种观点，即受 DM1 影响的 RI 患者表现出较温和的表型，其缺陷模式与 PR 患者相同，表明疾病过程相似。