Myotonic dystrophy type 1 as a cancer predisposition syndrome: A case report of quadruple primary malignancies with review of the literature.

Background: Myotonic dystrophy type 1 (DM1) is the most common adult-onset muscular dystrophy and is increasingly recognized as a cancer predisposition syndrome, with 2- to 8.5-fold elevated risks of endometrial, ovarian, thyroid, and colorectal cancers. Evidence on the oncological management of DM1 patients-including perioperative care, chemotherapy tolerability, and cancer surveillance-remains scarce. Case presentation: A 56-year-old woman with DM1 developed four primary malignancies over 16 years: papillary thyroid carcinoma at age 40, breast carcinoma at age 49, and synchronous endometrial carcinoma and low-grade serous ovarian carcinoma at age 56. Progressive respiratory muscle weakness necessitated tracheostomy and nocturnal ventilation from age 49, and DM1 was diagnosed at age 50. Three general anesthesia surgeries were completed without complications under multidisciplinary DM1-tailored perioperative protocols. For FIGO stage IIIB ovarian carcinoma, four cycles of paclitaxel-carboplatin chemotherapy were administered without dose reduction. First-degree atrioventricular block and left ventricular function remained stable, and treatment was discontinued for Grade 2 nausea rather than a DM1-specific toxicity. Conclusion: Standard-intensity multimodal cancer treatment was feasible in this DM1 patient with appropriate perioperative and cardiac monitoring. DM1 should be recognized as a cancer predisposition syndrome, and individualized surveillance strategies analogous to those used in hereditary cancer syndromes warrant further investigation.