[Clinical characteristics of SLC35A2 gene variants related congenital disorders of glycosylation typeⅡ].

Objective: To summarize the clinical characteristics of children with SLC35A2 gene variants related congenital disorders of glycosylation (SLC35A2-CDG), so as to improve the clinicians' understanding of this disease. Methods: Clinical data and gene detection results of 6 epilepsy children with SLC35A2 gene variants were treated in the Department of Pediatrics Peking University First Hospital from April 2019 to February 2020 were analyzed retrospectively. Results: Six children with SLC35A2 gene variants were identified, including 1 male and 5 females. The onset age of seizure was 5.5 (ranged from 2 to 20) months. All 6 cases had epileptic spasms, 2 cases had focal seizures, 2 cases had myoclonic seizures, 1 case had tonic seizures and 1 case had generalized tonic-clonic seizures. All patients with SLC35A2 gene variants were diagnosed as infantile spasm with developmental delay. Four cases had microcephaly, 4 cases had micro skeletal abnormalities, 3 cases had hypotonia and facial dysmorphism, 2 cases had inverted nipples. Visual abnormality, auditory anomaly, congenital cardiac disease and feeding difficulty were observed in one patient. The electroencephalography showed hypsarrhythmia in 6 patients. The brain magnetic resonance imaging (MRI) showed thinning of corpus callosum in 3 patients, delayed myelination in 2 patients and normal brain MRI in 3 patients. There were 2 cases of in-frame deletions, 1 case of missense variant, 1 case of splice site variant, 1 case of 2.14 kb deletion in Xp11.23 (only containing SLC35A2 gene) and 1 case of SLC35A2 gene mosaicism. All 6 cases had de novo variants. The last follow-up age ranged from 18 to 52 months. One patient was seizure free and 5 patients still had frequent seizures after treatment with antiepileptic drugs. Conclusions: SLC35A2 gene variants are mainly de novo variants. The characteristics of patients with SLC35A2-CDG are seizures and developmental delay, infantile spasms are most common diagnosis, micro skeletal anomaly, microcephaly, hypotonia, facial dysmorphism were accompanied features.