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.