Identifying Congenital Disorders of Glycosylation

Congenital Disorders of Glycosylation (CDG) constitute a diverse group of errors involved with protein glycosylation, a post-transcriptional modification that is essential for life. Due to the diversity of clinical presentations of CDG, they lead to multiple organ systems that are affected and delayed diagnosis. CDGs are usually diagnosed through whole exome sequencing, but carbohydrate deficient transferring (CDT) testing is a quick and cost-effective alternative that can be used as a screening tool for CDG. Although CDGs are rare and have varying presentations, there are two main subtypes, CDG I and CDG II; both of which we explored. We reviewed findings of seven confirmed cases of CDG (5 boys and 2 girls, with a mean age of 6.42 years at diagnosis) followed at Cook Children's Medical Center. We looked at the most common symptoms and age of diagnosis to determine which symptoms led to a diagnosis of CDG. The most frequent symptoms include ataxia (n=6), developmental delay (n=7), and hypotonia (n=7). Typically, within a year of documentation of these symptoms, a diagnosis was established either through CDT testing or WES. In cases that both CDT testing and WES were done, the CDT test proved to show results that correlated with WES. We believe that this is an important finding because when children present with ataxia, with or without developmental delay, and hypotonia, a CDT test can be ordered by a primary care physician as a rapid and economical screening tool that could lead to a quicker diagnosis of CDG.