The E2 story continues. There has been major progress in identifying the role of de novo mutations in infantile spasms and other epileptic encephalopathies. Over the last two years, more than 20 new genes for epileptic encephalopathies were discovered and we have good evidence suggesting that de novo mutations play a major role in these disorders. Moreover, we have gotten a good sense on how complicated it can be to call a de novo mutation pathogenic given the flood of rare genetic variants in the human genome. However, de novo mutations are not what we think about clinically when assessing a patient with new-onset epileptic encephalopathy. In a clinical setting, we are often concerned about underlying metabolic disorders, many of which are recessive. Accordingly, we felt that the next task of the E2 consortium was to assess the role of inherited variants in epileptic encephalopathies. Just to tell you in advance, it is not as easy as it sounds.
This week in epilepsy genetics. The following publications might be relevant for you, as they demonstrate what happened in the field of epilepsy genetics in the last two weeks. The publications range from basic science studies in extracellular space to novel gene discoveries. I have added a brief comment to each of these studies. Continue reading
Pyridoxal 5’-phosphate (PLP). PNPO deficiency is a rare neurometabolic disease that presents with severe neonatal epilepsy responsive to pyridoxal phosphate. While the classical clinical presentation is well described, there might be milder versions of this potentially treatable neurometabolic disease that have not been recognized so far. In a recent publication in Brain, the phenotypic spectrum of PNPO deficiency is revisited. In addition to the classical neonatal phenotype, the authors identify patients with later onset and atypical response to pyridoxal phosphate. In addition, they identify a rare, potentially causative PNPO variant that probably gets stuck in most exome filtering pipelines. Continue reading
Pushing the reset button. The history of epilepsy genetics can broadly be distinguished into two major eras: the time before September 4th, 2012 and everything after this. September 4th, 2012 was the date that the first large genome-wide association study in IGE/GGE was published online in Human Molecular Genetics. Each of the >100 association studies in IGE listed in PubMed is now dated and needs to measure up against the current study, which will likely be remembered as the “EPICURE study”. The results of the EPICURE study are surprising and upset our conventional wisdom of what causes one of the most common forms of epilepsy. Continue reading