Two familial cases of infantile epileptic spasms syndrome associated with UDP‐glucose‐6‐dehydrogenase deficiency

Developmental and epileptic encephalopathies (DEEs) are severe forms of epilepsy characterized by seizure onset in infancy or childhood. The seizures are typically drug-resistant and often accompanied by significant alterations in the electroencephalogram (EEG). DEEs are associated with neurodevelopmental impairment, which can arise from both the epileptic activity itself and the underlying etiology, which is most often genetic in origin. We present the clinical and molecular features of two patients with DEE associated with a pathogenic variant in the UGDH gene. This gene encodes a protein that converts uridine diphosphate (UDP)-glucose into UDP-glucuronate, which plays a crucial role in the biosynthesis of glycosaminoglycans, essential components of the connective tissue and extracellular matrix. Both patients started with epileptic spasms associated with a pattern of hypsarrhythmia in the EEG at 4 months of age. Both developed global developmental delay and the physical examination revealed hypotonia and mildly dysmorphic features. In both families, there was another affected sibling with a similar clinical presentation, although genetic studies were not performed in one of these children. A homozygous pathogenic variant in the UGDH gene, NM_003359.4:c.131C>T - p.(Ala44Val), previously reported to be associated with the described phenotype, was identified.