A recurrent c.953A>C (p. Gln318Pro) variant in ALG11 causing congenital disorder of glycosylation in Turkish population.

Congenital disorders of glycosylation type 1p, one of the N-glycosylation defects, Asparagine-dependent glycosylation 11 (ALG11-CDG, #OMIM: 613,666), is a very rare type of autosomal recessive glycosylation defect that causes multisystem involvement and frequently presents with neurological symptoms such as epilepsy and neuromotor developmental delay. In this study, we aimed to present three Turkish patients from three unrelated families with the recurrent variant in the ALG11 gene, along with their clinical and genotypic findings, and to compare them with other cases described in the literature. Three patients from three unrelated families were identified who were comprehensively evaluated with clinical examination, laboratory tests, and imaging studies. The whole exome sequencing (WES) with copy number analysis was performed. The identified variants were confirmed in the proband and parents using Sanger sequencing. Common clinical features of the patients included refractory epileptic seizures, developmental delay, and microcephaly, consistent with the literature. Developmental and Epileptic Encephalopathy starting in the first year of life and burst suppression pattern observed in electroencephalogram are among the important clinical features. WES analysis revealed a homozygous NM_001004127.3: c.953A > C (p. Gln318Pro) missense variant in the ALG11 gene in all three patients. This study presents the clinical and genetic features of three Turkish patients with the ALG11-CDG subtype, which has been previously described in the literature; it reinforces the current knowledge on phenotypic diversity by comparisons with similar cases. In addition, the role of WES in the diagnosis of rare CDG subtypes has been demonstrated once again.