Fading Muscle and a Flaccid Bladder: Atonic Bladder in a Case of Myotonic Dystrophy—A Case Report

Background Myotonic dystrophy Type 1 (DM1) is a multisystem genetic disorder characterised by progressive muscle weakness along with ocular, cardiac and endocrine abnormalities. However, detrusor underactivity manifesting as urinary retention is an under-recognised and rarely reported complication. Purpose To highlight a case of urinary retention caused by detrusor muscle underactivity in a young female with classic features of DM1, highlighting the need for early recognition and management of this rare but significant manifestation. Methods This case is of a 31-year-old female with urinary retention due to detrusor muscle underactivity, which is an under-recognised complication of DM1. The patient had classical features including grip myotonia, frontal balding, ptosis, intellectual impairment and early cataract changes. Uroflowmetry and significant post-void residual volume confirmed an atonic bladder. Elevated creatinine phosphokinase levels prompted electromyography, which demonstrated myotonic dive bomber discharges, and genetic testing identified pathogenic CTG trinucleotide repeat expansion in the myotonic dystrophy protein kinase ( DMPK ) gene. Result The patient was treated initially with clean intermittent catheterisation and Bethanechol (muscarinic agonist), then switched to indwelling urinary catheterisation due to improper technique. However, the risk of recurrent urinary tract infections remains a concern. Carbamazepine improved grip myotonia. Conclusion This case highlights the importance of the recognition of urinary retention as an important complication of DM1 and early recognition and treatment to prevent complications like recurrent urinary tract infections.