Fatal familial insomnia presenting with agrypnia excitata and very low atonia index level: A case report and literature review.

RATIONALE

Fatal familial insomnia (FFI) is a human prion disease that is characterized by sleep-wake cycle deterioration, loss of slow-wave sleep, and motor overactivation over the daily 24-hour period.

PATIENT CONCERNS

Here, we report the case of a 57-year-old man who had an irregular sleep-wake cycle and exhibited frequent movements and vocalizations during sleep.

DIAGNOSES

Video-polysomnography showed disrupted sleep structure, rapid alternation between sleep stages, and an absence of sleep spindles and slow-wave sleep. Moreover, body movements persisted throughout the entire sleep period, including rapid eye movement (REM) sleep. The atonia index was very low (<0.025) during REM sleep. Genetic testing revealed a prion protein gene mutation at codon 178, and the patient was diagnosed with FFI.

INTERVENTIONS

We tried to treat with amantadine, doxycycline, and immunotherapies, but the disease progressed.

OUTCOMES

Sleep disturbance is the most frequent and essential symptom of FFI.

LESSONS

FFI is difficult to diagnose due to the low sensitivity of diagnostic tools. Diagnoses can be further supported by better knowledge of typical polysomnographic findings.