Objective:To explore the clinical and genetic features in a case of fatal familial insomnia (FFI).Methods:A case of 39 years old woman diagnosed as progressive supranuclear palsy based on the preliminary manifestation of imbalance and frequent falls was reported. The clinical features, imaging characteristics, electroencephalogram and polysomnography of the patient were analyzed, and the blood samples from the patient were collected for the sequencing of prion protein (PRNP) gene.Results:This patient is a middle-aged woman, whose clinical manifestations were posture instability and retropulsion, rapid progressive dementia and dysarthria, sleep-related dyspnea and laryngeal stridor, with autonomic symptoms of hypertension, sweating, tachycardia and irregular breathing. The results of PRNP gene sequencing revealed that the mutation of gene D178N/129M was detected.Conclusions:Laryngeal stridor plays an important role in the diagnosis of FFI. Posture instability and retropulsion are relatively rare in the FFI clinical symptom spectrum. Here, a case of FFI presenting with posture instability and retropulsion during the early stage with Met/Met at the polymorphic codon 129 is reported in China.