A case of early onset epileptic encephalopathy with de novo mutation in SLC35A2: Clinical features and treatment for epilepsy

Abstract

Introduction: Mutations of SLC35A2 that encodes Golgi-localized Uridine diphosphate (UDP)-galactose transporter at Xp11.23 lead to congenital disorders of glycosylation (CDG). Although patients with CDG generally have diverse systemic symptoms, patients with a SLC35A2 mutation manifest predominantly disorders of the central nervous system (CNS).

Case report: A female infant aged 12months was referred to our center because of intractable seizures. The patient was born with birth weight of 3228g after 40weeks of unremarkable gestation. At the age of 2months, she had partial seizures evolving to epileptic spasms. Her electroencephalogram showed hypsarrhythmia. Her seizures were refractory to antiepileptic drugs. At referral to our center at 12months, she had developmental delay (no head control), widely spaced inverted nipples, external strabismus, and bilateral heterochromia of irises. Blood examinations were normal. Brain magnetic resonance imaging findings included cerebral and cerebellar atrophy, thinning of the corpus callosum, and arachnoid pouch. Whole-exome sequencing detected a de novo frameshift mutation c.950delG (p.Gly317Alafs*32) at exon 4 in SLC35A2. Seizures subsided after the second adrenocorticotropic hormones (ACTH) therapy at 18months. At the age of 36months, although she had intellectual disability with no meaningful words, she was seizure-free and was able to sit without support and showed smiling face a lot.

Conclusion: This report reviewed the clinical features of patients with a SLC35A2 mutation. ACTH therapy may be effective for refractory epilepsy in these patients.

Keywords: ACTH therapy; CDG; Early onset epileptic encephalopathy; SLC35A2; Skewed X-inactivation.