To the Editor In their article, Angus-Leppan et al1 presented a comprehensive and highly interesting report of a 68-year-old patient exhibiting a rapidly progressing array of symptoms including insomnia, personality change, myokymia, and eventually cognitive decline. As concluded by the authors, Morvan syndrome2 was suspected, and indeed, serum antibodies to the voltage-gated potassium channel complex were found. Brain biopsy findings were conclusive, with definite Creutzfeldt-Jakob disease (CJD). The combination of CJD and antibodies indicating a possible treatable immune-mediated encephalopathy is intriguing and raises concern of how to proceed with patients considered to have CJD especially as this combination does not seem to be a singularity. In 2012, we cared for a 67-year-old patient presenting with a 3-week rapidly progressive personality change and cognitive decline, as well as gait instability. Initially talkative, mildly disoriented, and ataxic, his condition deteriorated rapidly and he became bed bound, dysarthric, and dysphatic after 2 weeks; as time went on, he became mute and without any reaction to outside stimulus. No metabolic disturbances, besides known chronic renal failure, were detected. Repeated magnetic resonance imaging scans using diffusion-weighted imaging showed progressive extension of cortical hyperintensity bilateral parietooccipital with cortical ribbon sign highly compatible with the diagnosis of CJD.3 On electroencephalography, diffuse slowing without periodicity was seen. Results from repeated lumbar punctures did not show pleocytosis or elevated protein. Findings from neoplastic screening, including full-body positron emission tomography–computed tomography, were negative. Serum and cerebrospinal fluid antibody testing results were positive in 2 separate laboratories for Caspr-2 at a titer of 1:32. A course of high-dose steroids and plasmapharesis did not change the progression of the disease, and the patient died 4 weeks after hospital admission. The family refused brain biopsy or postmortem analysis. In concert with Angus-Leppan et al, the probability of 2 rare diseases in our patient was extremely low and magnetic resonance imaging did not support a diagnosis other than CJD. Unmasking of epitopes due to rapid neurodegeneration and secondary antibody appearance might explain the concurrent findings, but we argue that the low titer in both cases make it more probable that the antibodies were false positive and not involved in the disease pathophysiology in accord with their detection in control populations.4 Future research is urgently needed to clarify the relationship between the occurrences of antineural antibodies in CJD, especially to formulate screening and treatment guidelines and define cutoffs for antibody titers. Thus, more patients with rapid progressive dementia could be helped effectively, while others are spared from strenuous and highly expensive, yet ineffective, treatment.
Benninger FF, Steiner I. Creutzfeldt-Jakob Disease. JAMA Neurol. 2013;70(12):1588-1589. doi:10.1001/jamaneurol.2013.4412