Researchers from Canada presented the retrospective chart review of 2 siblings with ST3GAL3-related developmental and epileptic encephalopathy (DEE), a very rare condition that can evolve into Lennox-Gastaut syndrome

“Seizures . . . often occur in infancy and may present as epileptic spasms,” the researchers wrote in a report they published in the journal Epilepsia Open.

Read more about Lennox-Gastaut syndrome

“However, seizure onset may also occur outside of infancy with mixed seizure types and show good response to treatment with prolonged seizure freedom. Tremor may also be uniquely observed in this condition,” they wrote.

The cases presented are those of 2 brothers who had seizures, language and motor impairment, global developmental delay, and hypotonia, with tonic components that started between 2.5 and 5 years of age. The younger sibling also had tremors.

Carbamazepine treatment led to prolonged seizure-free periods in both children. 

Exome sequencing showed 2 novel pathogenic variants in the ST3GAL3 gene that were inherited in trans. 

The boys also underwent magnetic resonance imaging. This showed T2 hyperintensities and restricted diffusion in the brainstem and middle cerebellar peduncle in the older sibling. This phenotype was also described in 2 published cases.

The researchers also conducted a literature review and found 24 cases of ST3GAL3-related congenital disorder of glycosylation. Of these, 12 contained information about seizures, and 8 were diagnosed with epilepsy. 

The median age of the onset of seizures in these patients was 5.5  months. The most common type of seizures were epileptic spasms, seen in 67% of cases. 

A total of 4 children were diagnosed with infantile epileptic spasms syndrome and Lennox Gastaut syndrome. Most children continued having seizures in spite of being treated with anti-seizure medications.

Developmental and epileptic encephalopathy related to ST3GAL3 is an autosomal recessive condition characterized by epilepsy, motor and language impairments, behavioral difficulties, and intellectual disability.


Whitney R, Jain P, Ramachandran Nair R, et al. The epilepsy phenotype of ST3GAL3-related developmental and epileptic encephalopathy. Epilepsia Open. Published online April 17, 2023. doi:10.1002/epi4.12747