Fatal familial insomnia

This code represents a rare, inherited neurodegenerative prion disease characterized by progressive and intractable insomnia, dysautonomia, motor dysfunction, and cognitive decline. It is invariably fatal, typically within months to a few years of symptom onset, due to widespread neuronal loss, particularly in the thalamus.

Use this code for patients diagnosed with genetically confirmed or clinically evident fatal familial insomnia. Documentation should clearly indicate the diagnosis of this specific prion disease, often supported by genetic testing results (PRNP gene mutation) and a characteristic clinical presentation.

• Ensure documentation specifies "familial" to differentiate from other forms of insomnia or prion diseases.
• This code is highly specific; avoid using it for general insomnia or other neurodegenerative conditions without clear diagnostic confirmation.
• Consider sequencing this code as the primary diagnosis when it is the reason for the encounter or hospitalization.