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A Genome-wide Association Study of Myasthenia Gravis
Renton and colleagues identify genetic variants that alter susceptibility to myasthenia gravis by performing a genome-wide association study. They calculated P values for association between 8 114 394 genotyped and imputed variants across the genome and risk for developing myasthenia gravis using logistic regression modeling. Their genetic data provide insights into aberrant cellular mechanisms responsible for this prototypical autoimmune disorder. Editorial perspective is provided by Robert P. Lisak, MD, and Lisa Barcellos, PhD, MPH.
GBE1 Mutation in Manifesting Heterozygous Patients
Akman and coauthors explain the genetic change consistently associated with manifesting heterozygous patients with adult polyglucosan body disease. They studied 35 typical patients with adult polyglucosan body disease, of whom 16 were heterozygous for the well-known c.986A>C mutation in the glycogen branching enzyme gene (GBE1) but harbored no other known mutation in 16 exons. They identified the deep intronic mutation, which acts as a gene trap.
Clinical Review & Education
Nonmydriatic Ocular Fundus Photography
Bruce and coauthors review the importance of ocular fundus examination, the limitations of direct ophthalmoscopy, and the relative merits of nonmydriatic ocular fundus photography in emergency neurologic diagnosis. They find that nonmydriatic ocular fundus photography is more sensitive than direct ophthalmoscopy in several settings. Nonmydriatic ocular fundus photography has notable advantages over direct ophthalmoscopy that likely outweigh its associated costs.
Primary Familial Brain Calcification
Tadic and colleagues provide a systematic literature review on the neuroimaging and clinical phenotype of genetically confirmed primary familial brain calcification (PFBC) and summarize known pathophysiological mechanisms, to improve and harmonize future phenotype description and reporting by addressing data gaps, and to develop uniform definitions for clinical characterization. They systematically searched the MEDLINE database among articles published from January 1, 2012, through May 31, 2014, for the 3 genes and selected 25 articles from all records (n = 75) and from sources cited in the reference lists. For future analyses, they provide a minimal data set that can be used for systematic clinical and imaging data collection in PFBC and that will also improve informed counseling of patients.
GluN3A in Huntington Disease
Wesseling and Pérez-Otaño indicate that accumulating evidence suggests that synaptic dysregulation may be involved in Huntington disease (HD), and the earliest known deficit is hyperfunction of glutamate-type N-methyl-d-aspartate receptors (NMDARs) in the selectively vulnerable medium spiny neurons of the striatum. They state that loss of PACSIN1 and consequent gain of GluN3A function reactivate a synapse pruning mechanism that is important during development but harmful when active at later stages. They report that suppressing the GluN3A reactivation corrected the NMDAR hyperfunction and prevented the full range of HD signs and symptoms in mouse models, encouraging efforts to develop GluN3A-selective antagonists and/or explore alternative therapeutic approaches to block GluN3A expression.
Highlights. JAMA Neurol. 2015;72(4):379. doi:10.1001/jamaneurol.2014.2841
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