1. Introduction
Developmental encephalopathy (DE) is associated with developmental impairment, intellectual disability, and other neurological disorders such as epilepsy and movement disorders.1 DE has developmental consequences arising directly from the effect of genetic variants. The clinical features of patients with DE overlap with those of many neurodevelopmental disorders, and one disorder is difficult to distinguish from the others.
FOXG1 syndrome is one of the DEs, caused by a loss-of-function variant of FOXG1 , that encodes a brain-specific transcriptional factor critical for forebrain development.2,3 Patients with FOXG1 syndrome show microcephaly, hyperkinetic movement disorder, severe psychomotor delay without regression, and characteristic brain imaging findings.2,5 Because hyperkinetic movement disorders commonly develop by 1 year of age, they are proposed as a diagnostic marker for FOXG1 syndrome.5
Here, we report two cases of pyruvate dehydrogenase complex (PDHC) deficiency with clinical symptoms and brain imaging findings reminiscent of FOXG1 syndrome. They exhibited hyperkinetic involuntary movements and hand stereotypies, which are unusual for PDHC deficiency.6 This study demonstrates phenotypic overlap between PDHC deficiency and FOXG1 syndrome.