AbstractBackgroundDementia with Lewy bodies (DLB) is a neurodegenerative disorder characterized by cognitive decline, fluctuating attention, visual hallucinations, and sleep disorders, sometimes with signs of parkinsonism. Pathological evaluation reveals deposition of abnormally metabolized alpha‐synuclein, termed Lewy bodies. Clinical signs of DLB may be misdiagnosed in young patients with coexisting psychiatric disorders. A 43‐year‐old left‐handed man with a history of chronic paranoid schizophrenia, controlled with haloperidol, paroxetine, quetiapine, and clonazepam, presented with a 3‐year history of declining short‐term memory and concentration. He had a twin brother who was diagnosed with DLB and passed away at 40 years of age.MethodsThe patient was evaluated with serum laboratory tests to evaluate for metabolic abnormalities, infection, and heavy metal toxicity, including complete blood count, comprehensive metabolic panel, vitamin B12, folate, thyroid stimulating hormone, copper, and zinc. MRI Brain and subsequent PET‐FDG Brain were also conducted.ResultsThe results of the serum laboratory tests were all normal. MRI Brain was notable for bilateral parieto‐occipital atrophy and minimal chronic microvascular changes. PET‐FDG Brain revealed hypometabolism in bilateral parietal and occipital regions, with a cingulate island sign, indicative of advanced dementia with Lewy bodies.ConclusionDementia with Lewy bodies is a form of dementia that can sometimes present at an early age, and can be associated with psychological comorbidities and genetic risk factors. Further study of this case will include screening for mutations in the GBA gene, which encodes the enzyme beta‐glucocerebrosidease, which is the most frequent genetic association with dementia with Lewy bodies. Counseling on diagnosis and prognosis has been provided to the patient and his family, and he is being managed with rivastigmine 1.5mg twice daily to help slow down cognitive decline.