We report a case of CSF1R-microglial encephalopathy associated with a rare intronic c.2654 + 1G>A mutation, featuring negative diffusion-weighted imaging (DWI) findings and a cerebrospinal fluid (CSF) biomarker profile indicative of Alzheimer’s disease-related changes, and we explore the associations between genetic mutations, CSF biomarker alterations, and neuroimaging manifestations. The gene discussed is CSF1R; the disease is early-onset autosomal dominant Alzheimer disease.