Molecular diagnosis of a Chinese pedigree with α-mannosidosis and identification of a novel missense mutation.

α-Mannosidosis storage disease is a rare autosomal recessive disease that is caused by a deficiency of the lysosomal enzyme α-mannosidase. In this article, a proband in China was preliminarily diagnosed as having α-mannosidosis by clinical symptoms, imaging examination, and enzyme assay. Definitive diagnosis was performed by directly sequencing the MAN2B1 gDNA and cDNA of the peripheral blood leukocyte from the patient. Finally, denaturing high-performance liquid chromatography screening, conservative analysis, and protein secondary structure prediction were used to identify the novel mutation. The results showed that the patient has compound heterozygous mutations in the MAN2B1 gene, c.856G>A (p.E286K, novel) and c.788C>T (p.P263L). Her parents are heterozygote that carry one of these two mutations respectively. Pathogenicity identification of the novel mutation showed that the p.E286K mutation is a disease-causing mutation. Our work enriches the human MAN2B1 gene mutation database. As far as we know, this research is thus far the first gene diagnosis case of a Chinese patient with α-mannosidosis.