Cognitive Impairment in Sjögren's Disease: Unmasking Alzheimer's Through CSF Biomarkers. A Case Report.

Cognitive impairment in Sjögren's disease (SD) is typically attributed to autoimmune mechanisms or small vessel disease. However, its overlap with neurodegenerative pathology remains poorly understood. We report a 74-year-old woman with clinically diagnosed SD presenting with progressive memory decline. She demonstrated severe amnestic deficits on neuropsychological testing and had a cerebrospinal fluid (CSF) profile consistent with Alzheimer's disease (AD), including low Aβ1-42 and elevated total tau and phosphorylated tau. MRI revealed only mild small vessel disease. This case highlights the diagnostic importance of CSF biomarkers in distinguishing neurodegenerative from autoimmune cognitive syndromes. Though the overlap may be coincidental, it raises the question of whether systemic inflammation in SD could contribute to AD pathogenesis. This case illustrates how neurodegenerative disease may be overlooked in patients with autoimmune conditions. In individuals with SD and persistent amnestic symptoms, biomarker testing can help distinguish Alzheimer's pathology from autoimmune cognitive syndromes and guide more accurate diagnosis and care.