Glycosylation-related disorders. The graph shows the cumulative number of human glycosylation disorders in various biosynthetic pathways and the year of their identification. In most cases, the year indicates the definitive proof of gene and specific mutations. In early years, discovery was based on compelling biochemical evidence. Now, discovery is often based on genomic DNA sequencing. In 2013 alone, a new genetically proven glycosylation disorder was reported, on average, every 2 weeks.