From Crisis to Cancer: Diabetic Ketoacidosis Unmasking a Malignancy of Unknown Origin.

Diabetic ketoacidosis (DKA) is a life-threatening metabolic emergency, but its presentation as the first sign of an occult malignancy is extremely rare, particularly when the primary site is unknown. We report such a rare case of a 37-year-old woman presenting with progressive headache and vomiting. Initial assessment demonstrated DKA with associated electrolyte disturbances, which were managed promptly, and neuroimaging - prompted by concern for raised intracranial pressure - unexpectedly revealed brain metastases. Despite extensive imaging, immunohistochemistry, and multidisciplinary review, no definitive primary site could be identified. She was diagnosed with cancer of unknown primary (CUP) and referred for whole-brain radiotherapy and palliative care. This case illustrates the rare but critical scenario in which an acute metabolic emergency, such as DKA, unmasks an aggressive metastatic malignancy. The incidental detection of brain metastases in the absence of an identifiable primary tumour adds further diagnostic complexity. Early recognition of red flags, timely imaging, and multidisciplinary coordination are essential for guiding diagnosis and management.