Fatal familial insomnia preliminarily diagnosed as frontotemporal dementia: a case report and literature review

Abstract

Objective To explore the clinical, imaging, genetic features in a case of fatal familial insomnia (FFI), and review related literatures. Methods A case of middle-aged woman diagnosed as frontotemporal dementia based on the preliminary manifestation of abnormal mental behavior was reported. The clinical features, imaging characteristics, electroencephalogram and polysomnogram of the patient were analyzed, and the blood samples from the patient and some of her familial members were collected for the sequencing of prion protein gene (PRNP). Results This patient was a middle-aged woman, whose clinical manifestations were abnormal mental behavior, rapid progressive dementia and intractable insomnia, abnormal night sleep behavior and laryngeal stridor. Brain MRI indicated frontotemporal lobe atrophy. Non-sleep disturbance was observed in polysomnography. The cerebrospinal fluid was negative for 14-3-3 protein. The results of PRNP sequencing revealed that the mutation of gene D178N/129M was detected. Conclusions Detection of PRNP plays an important role in the diagnosis of FFI. Patients suspected of FFI in clinic should be detected for genetic testing. Whether the frontotemporal lobe atrophy was caused by FFI or concurrent with FFI remains to be further verified. Key words: Frontotemporal dementia; Insomnia, fatal familial; Prions