Phases. Today is Rare Disease Day. I would like to use this opportunity to explain some of the phenotype science that is critical for rare diseases. In contrast to common disorders, rare diseases face an unusual challenge. Once identified, the overall rareness of these condition poses the question of where phenotypes begin and where they end. For rare genetic disorders, is the phenotype of the first individual identified with a rare disease characteristic, or is there a larger spectrum that we should be aware of? Enter the various approaches to phenotype science that aim to decipher the full depth of clinical features associated with rare diseases. In order to understand the various approaches to rare diseases phenotypes, I would like to suggest a somewhat unusual analogy: phenotypes are like water.
Looking back. Admittedly, I have not written an end-of-the-year review for a quite some time. However, there were a few notable moments in epilepsy genetics in 2021 that I think were worth remembering. The second year of the COVID-19 pandemic started out as a year of recovery and readjustment, only to run into unanticipated supply chain issues and novel COVID variants hanging over our transition into 2022. The scientific community was affected by these developments in different ways that made progress of science somewhat unpredictable and uneven. 2021 was the year when the phrase “unprecedented times” became stale and overused. Here are five things to remember from 2021, which will be remembered as part of a transitional phase in epilepsy genetics. Continue reading
HPO. SCN2A-related disorders represent one of the most common causes of neurodevelopmental disorders and developmental and epileptic encephalopathies (DEE). However, while a genetic diagnosis is easily made through high-throughput genetic testing, SCN2A-related disorders have such a broad phenotypic range that understanding the full scale of the clinical features has been traditionally difficult. In our recent study, we used a harmonized framework for phenotypes based on the Human Phenotype Ontology (HPO) to systematically curate phenotypic annotations in all individuals reported in the literature and followed at our center, a total of 413 unrelated individuals. Mapping phenotypic data onto 10,860 terms with 562 unique concepts and applying some of the computational tools we have developed over the last three years, we were able to delineate the phenotypic range in unprecedented detail. SCN2A is now the first DEE with all available data systematically curated and harmonized in a computable format, allowing for entirely novel insights. Continue reading
Semantic similarity. The phenotype era in the epilepsies has now officially started. While it is possible for us to generate and analyze genetic data in the epilepsies at scale, phenotyping typically remains a manual, non-scalable task. This contrast has resulted in a significant imbalance where it is often easier to obtain genomic data than clinical data. However, it is often not the lack of clinical data that causes this problem, but our ability to handle it. Clinical data is often unstructured, incomplete and multi-dimensional, resulting in difficulties when trying to meaningfully analyze this information. Today, our publication on analyzing more than 31,000 phenotypic terms in 846 patient-parent trios with developmental and epileptic encephalopathies (DEE) appeared online. We developed a range of new concepts and techniques to analyze phenotypic information at scale, identified previously unknown patterns, and were bold enough to challenge the prevailing paradigms on how statistical evidence for disease causation is generated. Continue reading
EMR. When we consider the natural history of rare diseases like the genetic epilepsies, we typically think about a lack of longitudinal data that contrasts with the abundant genetic information that is available nowadays – the so-called phenotyping gap. We typically suggest that we need to obtain this information in future prospective studies to better understand long-term outcome, response to medications, and potential early warning signs for an adverse disease course. However, a vast amount of clinical data is collected on an ongoing basis through electronic medical records (EMR) as a byproduct of regular patient care. In a recent study, our group built tools to mine the electronic medical records to assess the disease history of 658 individuals with known or presumed epilepsies using clinical information collected at more than 62,000 patients encounters across more than 3,200 patient years. Here is a brief summary of our first study on EMR genomics, an untapped resource that has the potential to improve our understanding of the genetic epilepsies. Continue reading
Early-onset epilepsies. In recent years, we have discovered several causative genes for severe epilepsies beginning in the first year of life, including KCNQ2, SCN2A, and STXBP1. Several studies have reported a high yield of diagnostic genetic testing, including NGS panel approaches and whole exome sequencing, particularly in patients with seizure onset in the neonatal period where detection rates are often reported to be above 50%. Two recent studies add to the growing pile of evidence that genetic testing, and in particular NGS-based testing methods, are valuable in the diagnostic workup of children presenting with seizures early in life. Will these two studies help push us towards a new consensus regarding genetic testing in epilepsy?
FamilieSCN2A. On July 14th and 15th, Ingo and I had the pleasure of speaking at the FamilieSCN2a Annual Family and Professional Conference, which was hosted at the DuPont Children’s Hospital in Wilmington, Delaware. This meeting brings together families of children and young adults with SCN2A-related disorders and medical professionals and scientists working in the field, with the purpose of sharing information, learning from one another, and moving the field forward. This post won’t be a comprehensive recap of all that was discussed, since we heard from a broad range of professionals including therapists, electrophysiologists, epidemiologists, neurologists, and geneticists and it would be nearly impossible to sufficiently summarize everything. But I did want to share some of my impressions and thoughts. Here my five things I learned at the FamilieSCN2a Conference. Continue reading
Heterogeneity. The diversity of clinical presentations and responses to anti-epileptic drugs (AEDs) has posed a major obstacle in developing strategies to treat patients with SCN2A-related epilepsies. While the literature provides multiple examples of single case reports with favorable responses to various AEDs, the broad range of disease presentations and known or presumed effects on channel function has made it extremely difficult to extrapolate findings from one patient to another. In a recent publication in Brain, we reviewed the largest cohort of patients with SCN2A-related neurodevelopmental disorders so far, including a subset of patients with detailed phenotypic data over time. With this data, we were able to find support for the hypothesis that age of seizure onset correlates with the functional effect of the mutations and the response to common anti-epileptic medications, taking a first step towards understanding the SCN2A mystery. Continue reading
SCN2A. Last Thursday, I hopped on a plane to Chicago to join the first FamilieSCN2a Foundation Conference. SCN2A, one of the most common genes in genetic epilepsies, has emerged as a gene with a broad range of phenotypes, which makes understanding this gene relatively complicated. I am very happy that the SCN2A community is currently coming together to provide a platform for patient initiatives and connections to clinicians and researchers. Here is my list of five things I learned about the genetic shape-shifter in Chicago. Continue reading
Gene panels. Epilepsy gene panels have emerged as the first line genetic test for most suspected genetic epilepsies. Gene panels for childhood epilepsies are among the most common genetic tests ordered in a pediatric setting. While the role of gene panel testing is well established, the ideal design of gene panels remains an ongoing issue. A recent publication in the Journal of Medical Genetics provides additional evidence for the role of gene panel analysis in patients with genetic epilepsies. There are three aspects of this study that are particularly noteworthy. Continue reading