LEWY body dementia (LBD) can be especially difficult to identify in patients with a long history of psychiatric illness, where overlapping neuropsychiatric and motor symptoms may mask its emergence. A recent case illustrates how the condition can remain undetected for years when overshadowed by an existing diagnosis.
A 78-year-old woman with a 48-year history of paranoid schizophrenia was admitted with a sudden behavioural and functional decline. She presented with heightened agitation, incoherent speech, visual hallucinations, self-harm, reduced responsiveness, and motor impairment. Despite being on therapeutic doses of haloperidol, she showed hypersensitivity to antipsychotics and worsening extrapyramidal side effects.
Her progressive deterioration prompted repeated multidisciplinary team reviews. Clinicians noted marked cognitive fluctuations and motor changes inconsistent with her long-standing psychiatric profile. Although neuroimaging could not be performed due to her condition, her evolving symptoms fulfilled the clinical criteria for LBD. The absence of radiological evidence reinforced the importance of clinical judgment in diagnosing neurodegenerative disease in patients unable to undergo imaging.
The case underscores the danger of diagnostic overshadowing, where new neurological signs are attributed to an existing psychiatric disorder, and anchoring bias, where clinicians remain fixed on an earlier diagnosis. Without regular reassessment, underlying conditions such as LBD may be missed, resulting in delayed or inappropriate care.
Given her frailty and poor physiological reserve, she was transitioned to a palliative care pathway. The authors stress the need for vigilance when evaluating new motor and cognitive symptoms in patients with chronic psychiatric illness, as timely recognition of LBD can guide more accurate diagnosis, tailored treatment, and compassionate end-of-life planning.
Reference:
Iqbal A et al. A challenging diagnostic process: A case of Lewy body dementia in long-standing schizophrenia. Case Reports Cureus. 2025;17(8):e89967.
