The high pace of gene discovery has resulted in thrilling advances in the field of epilepsy genetics. Clinical testing with comprehensive gene panels, exomes, or genomes are now increasingly available and have led to a significant higher diagnostic yield in early-onset epilepsies and enabled precision medicine approaches. These have been instrumental in providing insights into the pathophysiology of both early-onset benign and self-limited syndromes and devastating developmental and epileptic encephalopathies (DEEs). Genetic heterogeneity is seen in many epilepsy syndromes such as West syndrome and epilepsy of infancy with migrating focal seizures (EIMFS), indicating that two or more genetic loci produce the same or similar phenotypes. At the same time, some genes such as SCN2A can be associated with a wide range of epilepsy syndromes ranging from self-limited familial neonatal epilepsy at the mild end to Ohtahara syndrome, EIFMS, West syndrome, Lennox–Gastaut syndrome, or unclassifiable DEEs at the severe end of the spectrum. The aim of this study was to review the clinical and genetic heterogeneity associated with epilepsy syndromes starting in the first year of life including: Self-limited familial neonatal, neonatal-infantile or infantile epilepsies, genetic epilepsy with febrile seizures plus spectrum, myoclonic epilepsy in infancy, Ohtahara syndrome, early myoclonic encephalopathy, West syndrome, Dravet syndrome, EIMFS, and unclassifiable DEEs. We also elaborate on the advantages and pitfalls of genetic testing in such conditions. Finally, we describe how a genetic diagnosis can potentially enable precision therapy in monogenic epilepsies and emphasize that early genetic testing is a cornerstone for such therapeutic strategies.

52Background: Glycosylphosphatidylinositol Biosynthesis Defects (GPIBDs) cause a group of 53

ABBSTRACTDYRK1A-related intellectual disability (ID) is among the most frequent monogenic form of ID. We refined the description of this disorder by reporting clinical and molecular data of forty individuals with ID harboring DYRK1A variants. We developed a combination of tools to interpret missense variants, which remains a major challenge in human genetics: i) a specific DYRK1A clinical score, ii) amino acid conservation data generated from one hundred of DYRK1A sequences across different taxa, iii) in vitro overexpression assays to study level, cellular localization, and kinase activity of DYRK1A mutant proteins, and iv) a specific blood DNA methylation signature. This integrative approach was successful to reclassify several variants as pathogenic. However, we questioned the involvement of some others, such as p.Thr588Asn, yet reported as pathogenic, and showed it does not cause obvious phenotype in mice, emphasizing the need to take care when interpreting variants, even those occurring de novo.

A 50 year old rock climber sustained a bilateral rupture of the distal biceps brachii tendons. He retained some flexion power in both arms but minimal supination, being weaker on the non-dominant right side. As the patient presented late, with retraction and shortening of the biceps muscle bellies, reconstruction was carried out using fascia lata grafts on both sides. Because of residual weakness on the left (dominant) side, three further surgical procedures had to be carried out to correct for elongation of the graft. A functionally satisfactory outcome, comparable with that on the right side, was eventually obtained. In summary, bilateral fascia lata grafts to bridge the gap between the retracted biceps bellies and the radial tuberosities were successful in restoring function and flexion power to the elbow. Despite being the stronger side, the dominant arm did not respond as well to the initial surgery. This may be due to overuse of this arm after the operation.

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