The sequence variant c.1830+1G>C is located in the donor splice site of intron 14 and interferes with the splicing process. In fibroblasts, the variant causes an in-frame deletion of exon 14 from the transcript (r.1645_1830del186), and is predicted to result in a truncated, non-functional protein (p.Val549_Glu610del). This variant is the second most common alpha-mannosidosis causing variant and accouints for about 6 % of the reported disease alleles.