Sudden Death Caused by Bilateral Diaphragmatic Eventration in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1, or dystrophia myotonica type 1 (DM1), is a multisystem disorder inherited in an autosomal dominant manner. It is caused by a CTG tri-nucleotide expansion in the 3'-untranslated region (3'-UTR) of the dystrophia myotonia protein kinase ( DMPK ) gene. Core clinical features include progressive skeletal muscle weakness, myotonia, and systemic complications, with premature mortality most often due to respiratory or cardiac dysfunction. We report the case of sudden death in a 48-year-old woman with a prior clinical diagnosis of DM1, who had not undergone adequate neuromuscular evaluation or surveillance. Postmortem examination revealed severe bilateral diaphragmatic eventration and restrictive lung pathology, consistent with severe respiratory compromise. The diagnosis of DM1 was confirmed at autopsy through gross and histologic findings, supported by molecular testing during the medicolegal autopsy. This case highlights the underappreciated risk of fatal respiratory failure in DM1, particularly in patients lacking longitudinal cardiopulmonary monitoring. The case also represents an example of a rarely reported autopsy finding in adults dying from DM1-bilateral diaphragmatic eventration.