Explosive onset non-epileptic jerks and profound hypotonia in an infant with Alpers-Huttenlocher syndrome

Alpers-Huttenlocher syndrome (AHS), first described over 80 years ago is an autosomal recessive neurodegenerative disorder characterised by the triad of refractory seizures, neuro-developmental regression and hepatic failure. AHS is now known to be caused by mutations in the gene encoding the catalytic subunit of polymerase gamma (POLG1), an important mitochondrial DNA replication enzyme. The phenotypes of AHS and other phenotypes caused by POLG1 mutations have expanded to include atypical and often diagnostically elusive presentations with variable age of onset, disease severity and progression. Awareness of the individual expression and wider constellation of signs is important for diagnosis. Epileptic seizures in AHS are usually partial, secondary generalised tonic-clonic or myoclonic, with occipital lobe predilection. In many cases, children present with refractory status epilepticus or continuous focal motor seizures (epilepsia partialis continua). A distinctive electroencephalogram (EEG) pattern, posterior rhythmic high-amplitude delta with superimposed polyspikes (RHADS) is very suggestive of the diagnosis. We describe with video-EEG, a previously normal infant who presented with explosive-onset profound hypotonia and bilateral non-epileptic jerks, ultimately found to have AHS. The presentation outlined has not been previously reported.