Cerebrospinal fluid real-time quaking-induced conversion test for sporadic Creutzfeldt–Jakob disease in an 18-year-old woman

RATIONALE Sporadic Creutzfeldt-Jakob disease (sCJD) mainly occurs in the elderly, with the peak age of onset ranging from 55 to 75 years. The symptoms of sCJD are not unique, and laboratory tests such as magnetic resonance imaging (MRI), electroencephalogram (EEG) and cerebrospinal fluid (CSF)14-3-3 protein have low sensitivity or specificity. Therefore, excluding treatable diseases and establishing a diagnosis could be difficult in young patients with suspected sCJD. Recently, real-time quaking-induced conversion (RT-QuIC) has been used in the diagnosis of sCJD, with more than 95% sensitivity and 100% specificity. PATIENT CONCERNS We report the case of an 18-year-old woman presented with cerebellar ataxia, blurred vision, rapidly progressive dementia, tremor and involuntary movements, urinary incontinence, mutism, and eventually myoclonus for 16 weeks. Brain MRI scans were unremarkable at the 4th and 8th week after initial symptom presentation, but showed hyperintensity in bilateral basal ganglia and cortical ribboning at the 16th week. Typical periodic bilateral triphasic sharp wave complexes on EEG did not appear until the 16th week after initial symptom presentation. DIAGNOSES Due to the young age of the patient and the originally unremarkable MRI and EEG findings, we first considered treatable diseases such as autoimmune encephalitis, infections, organic acidemias and toxication. However, extensive tests ruled out these diseases. When she was finally diagnosed with probable sCJD, we were unable to perform a brain biopsy. We confirmed the diagnosis by detecting the scrapie form of prion protein in the CSF using RT-QuIC. INTERVENTIONS Experimental treatments with corticosteroids, intravenous immunoglobulin and ganciclovir were given. OUTCOMES Experimental treatments were ineffective. The patient's parents discharged her from our clinic. LESSONS We present a case of probable sCJD with an early onset and a complex clinical picture confirmed by RT-QuIC. This case report suggests that RT-QuIC has great value for the diagnosis of atypical cases.