AN INSIGHT TO A RARE GENETIC DISORDER: FATAL FAMILIAL INSOMNIA

This review study was carried out to educate people about a rare genetic disorder that is fatal familial insomnia. Fatal familial insomnia (FFI) is an autosomal dominant inherited neurodegenerative disorder caused by mutation in the prion protein gene (PRNP) at codon 178 located in the short arm of chromosome 20 at position p13 responsible for making of prion protein. The disease-causing mutation consist of substitution from normal aspartic acid (Asp) to asparagine (Asn). The presence of methionine at codon 129 is distinct for FFI compared to valine at the same position in Familial Creutzfeldt -Jakob disease. The more aggressive variant has methionine (Met-Met) on the non-mutated allele compared to variant which has valine (Met-Val) [1]. Prion related diseases are Creutzfeldt-Jakob disease [11], Kuru [12], Grestmann straussler syndrome [13]. FFI is characterized by severe sleep disorder caused by psychiatric symptoms and vegetative symptoms [1] with motor dysfunction of sleep generation mechanism has been called as "Agrypnia excitata" [13]. Both familial and sporadic FFI can be evaluated by CSF studies, PSG, electroencephalogram, molecular genetic testing, biopsy and imaging [5]. FFI is diagnosed by PRNP Gene test. There is no cure for FFI and no standardized treatment protocols. Only symptomatic treatment is centered on relief and palliative cure along with investigational therapy and current therapy is monitored by accompanying with self-management [3]. The disease course lasts from 7-36 months with an average duration of 18 months leading to eventual death [1]. The review study carried out suggests the need for future research and clinical studies in patients with the disorder