Forkhead Box G1 Gene Haploinsufficiency: An Emerging Cause of Dyskinetic Encephalopathy of Infancy

Background: 14q12 deletions, including the Forkhead Box G1 (FOXG1) gene and point mutations of this gene, are associated with a complex encephalopathy described as a congenital variant of Rett syndrome. A mixture of jerks, athetosis, chorea, and dystonia is observed early in life in many patients. The aim of this article is to report on the spectrum of movement disorders associated with FOXG1 haploinsufficiency, as described in the literature. Patients and methods: We provide a review of the cases reported in the literature, adding two new patients. We searched for a comprehensive set of clinical features, including age at onset and semiology of the movement disorder, occurrence and type of stereotypies, and neurological outcome. Results: A total of 51 cases were included in our study. Nonepileptic abnormal movements occurred in 33 cases, often variably combined and presenting during the first year of life. Conclusion: The neurological phenotype of FOXG1 haploinsufficiency shows the features of a dyskinetic encephalopathy of infancy.