An elderly patient with dementia presenting euglycaemic ketoacidosis due to oesophageal stricture-associated eating habits.

An 85-year-old man with dementia was referred to our department because of problematic eating habits, which made it difficult to manage his diabetes mellitus. The patient exhibited euglycaemic ketoacidosis, with a clinical course and biochemical parameters more indicative of starvation ketoacidosis rather than diabetic ketoacidosis. After correcting the acid-base imbalance with dextrose-containing fluids, he attempted to resume oral intake; however, throat noises consistent with reflux were noted during food ingestion. Imaging and pathological studies revealed a stricture with wall thickening in the mid-oesophagus attributed to non-specific chronic oesophagitis. After receiving hypercaloric fluids to calm oesophageal inflammation, an endoscopic bougienage was performed, enabling oral intake and achieving appropriate glycaemic control with oral glucose-lowering agents. This case illustrates the importance of closely monitoring eating behaviours, which is crucial for identifying comorbid organic abnormalities, without being limited by cognitive bias in clinical reasoning that problematic dietary changes are highly prevalent in dementia patients.