A Challenging Diagnostic Process: A Case of Lewy Body Dementia in Long-Standing Schizophrenia

Lewy body dementia (LBD) is a progressive neurodegenerative disorder presenting with a wide range of cognitive, sleep, neuropsychiatric, motor, and autonomic symptoms. Diagnosing LBD in individuals with established psychiatric conditions, particularly chronic schizophrenia, presents significant challenges due to overlapping clinical features. This case report outlines a case of a 78-year-old woman with a 48-year history of paranoid schizophrenia, who on her last admission exhibited new behavioural and functional decline. This included increased agitation, incoherent mumbling, visual hallucinations, self-harming behaviour, motor symptoms, and reduced responsiveness. Over time, she became increasingly frail and was displaying signs of extrapyramidal side effects on therapeutic doses of haloperidol. Her presentation triggered regular comprehensive multidisciplinary team (MDT) discussions and reassessments, especially when the medical staff noted worsening motor symptoms, hypersensitivity to antipsychotics, and cognitive fluctuations. Although her primary psychiatric diagnosis had been schizophrenia for nearly five decades, the clinical evolution strongly indicated LBD, an emerging neurodegenerative process. Despite the absence of radiologic evidence, largely due to her condition, her new symptoms aligned with the diagnostic criteria for LBD. Subsequently, due to her poor physiological reserve, she was managed under a palliative care pathway. This case highlights the importance of periodic diagnostic reassessment in a patient with a long-standing psychiatric disorder. Without careful review, there is a risk of diagnostic overshadowing, where new symptoms observed are miscredited to a historical diagnosis. Additionally, anchoring bias can further add to the issue as clinicians become fixated on the initial diagnosis. As a result, differentiating between chronic psychosis and evolving neurodegenerative conditions like LBD is crucial to avoid inaccurate management and to develop appropriate care plans, especially in vulnerable patients.