Extending the Phenotype Related to SCN1A Gene: Arthrogryposis, Movement Disorders, and Malformations of Cortical Development

Background Expand the knowledge about the clinical phenotypes associated with pathogenic or likely pathogenic variants in the SCN1A gene. Methods The study was carried out in 15 patients with SCN1A variants. The complete phenotype of the patients was evaluated. A systematic search was carried out in the scientific literature for those unexpected symptoms. Results Ten patients showed a missense variant, whereas the remaining showed different loss-of-function variants. Twelve (80%) had Dravet syndrome. Two (13.3%) had Epilepsy with febrile seizures plus. Three (20%) presented an atypical phenotype. One of them was developmental and epileptic encephalopathy with arthrogryposis, the other Dravet syndrome and movement disorder, and lastly one patient had Dravet syndrome and malformations of the cortical development. Conclusion The exhaustive assessment of patients with pathogenic alterations detected in massive sequencing can help us to expand the phenotype, understand the etiopathogenesis associated with each genetic abnormality, and thus improve the prognosis and management of future patients.