Dissociation in circadian rhythms in a pseudohypersomnia form of fatal familial insomnia.

The authors present clinical, sleep, and neuroendocrine features of a patient with genetically confirmed fatal familial insomnia (D178N mutation with heterozygosity at codon 129 of the prion protein gene). The patient exhibited pseudohypersomnia behavior instead of insomnia. There was profound alteration in the sleep-wake cycle with a clear dissociation in the disappearance of circadian and neuroendocrine rhythms, findings unrelated to abnormalities in the hypocretinergic system.