A Case of Amyotrophic Lateral Sclerosis With Coexisting Maturity-onset Diabetes of the Young Type 5

We report the case of a 60-year-old Japanese woman with genetically confirmed maturity-onset diabetes of the young type 5 [MODY5; HNF1B (hepatocyte nuclear factor 1B)-MODY] who developed amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative disorder. MODY is a rare monogenic form of diabetes mellitus, typically associated with urogenital anomalies and pancreatic hypoplasia. At the age of 25, she was diagnosed with diabetes mellitus. The clinical findings, including bilateral renal cysts, agenesis of the pancreatic body and tail, and impaired insulin secretion without β-cell-specific autoimmune autoantibodies, suggested HNF1B-MODY. A 1.4-Mb hemiallelic deletion on chromosome 17q12 encompassing <i>HNF1B</i> was confirmed, and she was subsequently diagnosed with HNF1B-MODY. At age 59, she developed symptoms of a common cold, followed by dysarthria and limb weakness. The neurological examination revealed tongue fasciculations, spasticity, and hyperreflexia. Electromyography indicated widespread motor neuron degeneration, consistent with a diagnosis of definite ALS. Whole-exome sequencing revealed no known ALS-related pathogenic variants, and no ALS candidate genes were detected in the deleted region of 17q12. To our knowledge, this is the first reported case of concurrent ALS and HNF1B-MODY. While a direct genetic link is unclear, this co-occurrence may provide insights into the shared molecular pathways and warrants further investigation.