Background: Myotonic dystrophy (DM) is the most common muscular dystrophy in adults. Dominantly inherited CTG and CCTG repeat expansions in DMPK and CNBP genes cause DM type 1 and DM type 2, respectively. These genetic defects lead to abnormal splicing of different mRNA transcripts which are thought to be responsible for the multiorgan involvement of these diseases. In our and others' experience, the frequency of cancer in DM patients appears to be higher than in other muscular dystrophies and general population, and not uncommonly we encounter patients who have suffered more than one cancer. Thus, an increased frequency of specific cancer types (thyroid, endometrium, ovary, skin, eye, brain, colorectal, and testis) has been reported in DM1 patients on retrospective studies. The association between DM2 and cancer is less clear. Current consensus-based care recommendations for adults with DM1 and DM2 advise to follow the same cancer screening guidelines that are recommended for the general population. On the other hand, cancer screening recommendations vary among countries and do not include screening of some cancer types reported to be more frequent in DM patients.
Objective: To determine the frequency and type of cancers and benign tumors in our DM cohort of 168 DM1 patients and 56 DM2 patients.
Methods: A retrospective chart review of patients diagnosed with DM1 or DM2 from 2000 to 2020 at Massachusetts General Brigham was conducted. Demographics, clinical characteristics, and type of cancers and benign tumors, if present, were recorded.
Results: A total of 26 (15.5%) DM1 patients and 17 (30.3%) DM2 patients had at least one cancer, and two DM1 and five DM2 patients had more than one cancer. In addition to breast, skin and thyroid malignancies were the most frequent cancers in both DM1 and DM2 cohorts. Thyroid nodules were the most common benign tumor in this cohort. Pilomatrixoma was only reported in one male DM1 patient.
Conclusion: In addition to cancer screening guidelines for general population, and in alignment with other retrospective studies, DM patients may benefit from skin check and thyroid gland palpation as non-invasive and bedside tumoral screenings of these organs.