When Steroids Complicate the Diagnosis: Recurrent Steroid-Induced Psychosis, Severe Hyponatraemia With Generalized Tonic-Clonic Seizure, and Acute Lacunar Infarction During Treatment for Suspected Giant Cell Arteritis.

A 77-year-old woman with a history of palindromic rheumatism and a previous episode of steroid-induced psychosis was treated with high-dose prednisolone for suspected giant cell arteritis because of the risk of irreversible visual loss. Within days, she developed recurrent psychotic symptoms requiring hospital admission. During her admission, she experienced profound hypovolaemic hyponatraemia complicated by a generalized tonic-clonic seizure. Following correction of her sodium level, brain magnetic resonance imaging unexpectedly demonstrated an acute left basal ganglia lacunar infarction despite the absence of focal neurological deficits. The coexistence of recurrent steroid-induced psychosis, severe electrolyte disturbance, seizure, and acute cerebral infarction created a significant diagnostic challenge, prompting multidisciplinary involvement from rheumatology, neurology, stroke medicine, psychiatry, endocrinology, and general internal medicine. Further investigations, including CT angiography, cerebrospinal fluid analysis, autoimmune screening, and fluorodeoxyglucose positron emission tomography, were undertaken to evaluate for possible systemic or central nervous system vasculitis. This case highlights the importance of maintaining a broad differential diagnosis in patients receiving glucocorticoid therapy, particularly when neuropsychiatric symptoms coexist with metabolic and neurological abnormalities. It also illustrates the value of multidisciplinary assessment in distinguishing medication-related adverse effects from alternative or concurrent pathology.