CLDN5, the blood brain barrier, and alternating hemiplegia of childhood

AHC. Amongst the various episodic neurological disorders of childhood, alternating hemiplegia of childhood (AHC) is one of the most mysterious conditions. AHC is characterized by transient hemiplegic attacks and a wide range of other neurological features including dystonic attacks, seizures, neurodevelopmental features, and autonomic symptoms. Recurrent de novo variants in ATP1A3 represent the most common cause of AHC, even though a small subset of individuals have disease-causing variants in other genes. In a recent paper, de novo variants in CLDN5 were identified. In contrast to known causes of AHC, CLDN5 implicates an entirely new disease mechanism – disruptions of the blood-brain barrier. Continue reading

EuroEPINOMICS and the golden age of epilepsy gene discovery

Exome era. When a consortium disappears, where does it go and what does it leave behind? I realized last week that exactly 10 years ago, the EuroEPINOMICS Rare Epilepsy Syndrome (RES) consortium pushed the button for the second round of trio exome sequencing, a pivotal event in the history of epilepsy genetics that led to the discovery of more than a dozen genes for developmental and epileptic encephalopathies. The fact that this critical juncture in the history of epilepsy gene discovery went largely unnoticed lies within the nature of research consortia – they form, they work, and they disperse. However, as EuroEPINOMICS was formative for me as a junior researcher, I wanted to dedicate this blog post to the research consortia of the early 2010s and the golden era of epilepsy gene discovery, when I was a EuroEPINOMICS kid.

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Artificial intelligence in epilepsy – the rare disease perspective

Breckenridge. This week, our team attended the first conference for Artificial Intelligence in Epilepsy in Breckenridge, Colorado. I was honored to be one of the two speakers representing the epilepsy genetics field, trying to build the bridge between the impressive amount of research in machine learning and EEG analysis with our current progress and research efforts in the genetic epilepsies. In this blog post, I would like to summarize some of my impressions from this meeting and discuss two aspects where rare disease research and machine learning already intersect, namely seizure forecasting and virtual clinical trials.

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IRF2BPL in progressive myoclonus epilepsy – an unexpected phenotypic discovery

PME. The progressive myoclonus epilepsies (PME) are an important and distinct subgroup of genetic epilepsies. In contrast to many genetic epilepsies with a neurodevelopmental trajectory, the PMEs often follow a neurodegenerative course, which is characterized by a worsening myoclonus over time and frequently associated with cognitive decline. In a recent publication, protein-truncating variants in the intronless gene IRF2BPL were identified in two individuals with PME. However, in contrast to the relatively distinct nature of most other PME, the clinical presentation in IRF2BPL-related disorders is part of a phenotypic spectrum and emerges as one of the most usual phenotypic discoveries in the genetic epilepsies to date.

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Phenotypes are like water – Rare Disease Day 2023

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.

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The pebbles of Demosthenes – stuttering genetics in 2023

Zebra finches. Exactly one year ago, I wrote my last blog post on the genetics of stuttering and thought that it would be time for an update. Here, I would like to explore why stuttering is a truly neglected neurogenetic disorder and why we have made so little progress. In addition, I would like to give a brief update on where we are right now, looking at stuttering from the perspective of the wider pediatric neurogenetics field. In addition, we will unleash the power of EMR genomics to query the medical records of more than 52,000 individuals to find associated genes, and we will discuss a monogenic cause of familial childhood-onset fluency disorders that we did not expect to find. Here is a summary of the last 12 months in stuttering genetics. Continue reading

Why variants of uncertain significance need explanatoriness

ACMG. Imagine the following scenario: you identify a de novo variant in SCN1A in a young child with the typical clinical features of Dravet Syndrome. However, the lab returns the variant as a variant of uncertain significance. The variant is a missense variant that has never been seen before and the lab argues that they are simply applying the current variant classification criteria. Certainly, either the lab is wrong or the variant classification criteria are deficient. Shouldn’t this variant be a pathogenic variant? Your patient clearly has the typical clinical features that are very unlikely explained by anything but the de novo SCN1A variant. In fact, both assumptions are incorrect, but it is important to know the background. Here is a blog post on why variant classification is distinct from assessing whether variants are explanatory in a clinical context. And please allow me to introduce a neologism: explanatoriness. Continue reading

Anatomy, physiology, and the art of motorcycle maintenance

Zen. This weekend, I finished Robert Pirsig’s Zen and the Art of Motorcycle Maintenance. The unfinished task of reading this book has followed me through my entire academic career. It was initially given to me as a gift for being an anatomy tutor in medical school. Independently, I received it as a gift when I passed my German child neurology boards. I started this book several times, but never finished it, and reading this book took me 25 years. As my professor’s thoughts about various approaches to studying medicine have echoed with me since I was a student tutor, this book deserves its own blog post and an enquiry into values (as Pirsig would say) of anatomy versus physiology. Continue reading

CHD2 – here is what you need to know in 2023

Chromodomain. Today is International CHD2 Awareness Day and we are publishing this blog post in time for our CHD2 webinar where we present the result of a four-week sprint to analyze harmonized clinical data. We also updated our gene page on CHD2, which was long overdue. In addition to becoming a more well-known gene, here are three things to know about CHD2 in 2023. Continue reading

Precision medicine in the absence of outcomes

EMR. Genomic data is increasingly available for large patient cohorts. In parallel, healthcare is increasingly digitized and large amounts of data can easily be extracted and analyzed at the click of a button. In principle, this should provide tremendous opportunities to understand how epilepsy care can be personalized based on genetic factors. However, we quickly run into challenges. Obtaining information on seizure frequencies, for example, requires manual chart review. Trying to understand how a person’s genetic makeup affects responses to anti-seizure medications is therefore not possible in large healthcare systems where related questions in other diseases can increasingly be answered. Here is a brief overview of how we can meaningfully engage with clinical data when outcomes are simply not available. Continue reading