The familial form of the Creutzfeldt-Jakob disease (ffCJD) refers to a group of rare and severe neurodegenerative diseases associated with pathologic prion protein accumulation. The cause of disease is genetically determined. The disease has a continuously progressive course leading to death in 100% of cases. The symptoms of dementia dominate in the clinical picture. The authors describe a clinical case of subacute dementia in a 32-year-old patient. The disease had a progressive course. A preliminary diagnosis of ffCJD was established after neurological, psychiatric, genetic examinations and dynamic observation. The diagnosis met the following criteria of the Center for Disease Control and Prevention, CDC: progressive dementia, extrapyramidal disorders, absence of special EEG complexes, disease duration less than 2-3 years, confirmed genetic mutation in the prion protein gene, bilateral hyper intensive signals in the caudate nuclei region, the thalami on T2-weighted images (a 'honeycomb' symptom), atrophy of the cerebral cortex and cortex cerebelli on diffusion-weighted brain MRI (DWI). The patients died 3 years after the onset of the disease. The pathological signs of neuron spongiform degeneration as important characteristics of the disease were found at autopsy.