Clinical and genetic features of 13 patients with mucopolysaccarhidosis type IIIB: Description of two novel NAGLU gene mutations

Mucopolysaccharidosis type III B (MPS IIIB) is an autosomal recessive lysosomal storage disease caused by mutations in the NAGLU gene which codes the lysosomal enzyme alpha-N-acetylglucosaminidase. The major symptoms of the disease are cognitive and neurological defects. In this study, the molecular spectrums of 13 MPS IIIB patients were evaluated. Thirteen MPS IIIB patients from 11 families were included in this study. All patients were both clinically and molecularly diagnosed. NAGLU gene sequencing was performed using a next generation sequencing platform (Illumina MiSeq). Demographic, clinical and laboratory findings of the patients were obtained via the hospital records. Ten different mutations from the 13 MPS IIIB patients were identified. Eight of the 10 mutations were missense, one was splice site, and one large deletion was also observed. Two mutations c.509G>T (p.Gly170Val) and c.700C>G (p.Arg234Gly) have been defined for the first time in this study. Our study expanded the mutation spectrum of the NAGLU gene thereby contributing to the improved genetic counselling of MPS IIIB patients. Confirming the literature, missense mutations were also found to be the most common NAGLU mutations in our study.