GLUT1DS. Disease-causing variants in SLC2A1 are associated with a rare genetic neurometabolic condition known as GLUT1 Deficiency Syndrome (GLUT1DS). While GLUT1DS is typically diagnosed through molecular genetic testing, the diagnostic strategy in some cases includes lumbar puncture to measure cerebrospinal fluid (CSF) glucose to confirm the diagnosis. In a recent study, Mochel and collaborators performed a multicenter validation study of a blood-based biomarker for GLUT1DS. Here is a brief review on their publication and the utility of molecular biomarkers in GLUT1DS and genetic epilepsies more broadly.
What is the most common monogenic cause of epilepsy? This is a question we often ask students and trainees who rotate with us in our Epilepsy Neurogenetics Clinic. This is not meant to be a trick question, and the answer we previously sought was based largely on published studies, estimates of population frequency of individual genetic epilepsies, and our own clinical experience. And we are sometimes surprised by how skewed such a view can be. Now, a new study by Symonds and colleagues answers the question of population-incidence of common genetic epilepsy syndromes through a prospective population-based cohort study in Scotland. This study provides important data on risk factors that are more likely to predict a genetic diagnosis in infants and young children with seizures and answers the question of which genetic epilepsy is most common. I was initially surprised, but really not surprised at all, by the answer. Continue reading
Ketogenic. Several patients with Myoclonic Astatic Epilepsy (MAE) have a surprisingly positive response to the ketogenic diet, even after failing several antiepileptic medications. Given this observation, it is obvious to assume that SCL2A1 mutations play a significant role in MAE, and some earlier studies seemed to suggest that up to 5% of MAE patients carry SLC2A1 mutations. However, in a recent study, we failed to demonstrate a connection between SLC2A1 mutations and Myoclonic Astatic Epilepsy (MAE) in a large cohort of patients. Read more on why the genetics of MAE is an ongoing mystery and why we need a new approach to “keto-genetics”. Continue reading
Think metabolic. We have discussed de novo mutations as a cause of epileptic encephalopathies repeatedly on our blog. While there is emerging evidence that de novo mutations in established genes such as SCN1A or CDKL5 or novel genes including GNAO1 or CHD2 are a major cause of genetic morbidity in patients with epileptic encephalopathies, investigations for de novo mutations are not the immediate knee-jerk reaction in clinical practice. In fact, if a child presents with an epileptic encephalopathy, excluding inborn errors of metabolism (IEM) takes priority. While metabolic causes of epileptic encephalopathies are rare, they need to be excluded as some of these conditions are treatable. In a recent review in Molecular Genetics and Metabolism, van Karnebeek and colleagues review the 89 causes of intellectual disability that are potentially treatable. Many of these conditions also present with epilepsy. They present an updated diagnostic algorithm and provide an online resource for these conditions – in a nutshell, there is an app for that. Continue reading
Fall colors. Just a brief summary of how this post originated. Eckernförde is a small city north of Kiel and the weekly Sunday destination of my daughter and me because of the wave pool. This past Sunday, daylight saving and the fact that she didn’t like her dinner had confused the little girl, and we had been awake since 4AM. As a consequence, she fell asleep on the way, and I kept driving to let her sleep. We made it as far as Haddeby, and I used this time to mentally put a post together that I had been planning for some time. These are the three things that are often misunderstood with regards to epilepsy and genes. Continue reading
Autosomal recessive West Syndrome. Exome sequencing and other high-throughput sequencing technologies work best in the identification of recessive disorders. While many cases of West Syndrome are thought to be the result of de novo mutations, recessive inheritance is seen in a subset of patients. In a recent paper in Epilepsia, Edvardson and colleagues now report mutations in ST3GAL3 in a consanguineous Palestinian family with four affected individuals with West Syndrome. This report takes us deep into the chromosomal anatomy of the linkage region, raising the question at what point we can claim that a gene is found. Continue reading
Exome no more. Over the last 15 months, we have repeatedly discussed how exome sequencing or genome sequencing is applied to neurodevelopmental disorders in order to discover new candidate genes and to assess the role of known candidate genes. We have also wondered sometimes whether exome sequencing is the most straightforward approach. Now – outpacing the two large international consortia using exome sequencing in epileptic encephalopathies – a recent study in Nature Genetics uses a different approach to uncover the genetic basis in 10% of patients with epileptic encephalopathies. Targeted resequencing or gene panel analysis is a hybrid technology between candidate gene sequencing and next generation sequencing and focuses only on a subset of candidate genes. While their study provides a comprehensive overview over the genetics of rare epilepsy syndromes, it raises the question whether the era of large-scale exome sequencing is coming to a natural end. Continue reading