Also known as Polypeptide N-Acetylgalactosaminyltransferase 2 Deficiency
A very rare, multisystemic, inherited condition caused by an abnormal enzyme which disrupts O-glycosylation. Symptoms manifest during infancy and childhood, including global developmental delay, intellectual disability, behavioral abnormalities, epilepsy, insomnia, stunted growth, facial dysmorphism (abnormal difference in structure), decreased HDL-cholesterol, and white matter brain lesions.
GALNT2-CDG is a very rare inherited condition that affects multiple parts of the body. There are only 8 GALNT2-CDG patients from 5 families published in the medical literature.
Individuals with GALNT2-CDG typically develop signs and symptoms of the condition during infancy and childhood. Affected individuals exhibit global developmental delay, intellectual disability without language development, behavioral abnormalities, childhood onset epilepsy, chronic insomnia, decreased height, and white matter lesions on brain MRI scan. Laboratory abnormalities include low HDL-cholesterol.
GALNT2 initiates O-glycosylation, including specifically on ApoC-III. Therefore, screening for the disorder is performed looking at glycosylation of ApoC-III and patients have normal N-glycosylation, such as on transferrin screening, which is a very distinctive pattern. The ultimate diagnosis is genetic testing in blood. Individuals with GALNT2-CDG have two faulty copies of the GALNT2 gene.
Treatment and Prognosis
To date, there are no known specific treatment options for GALNT2-CDG. Treatment is aimed at the management of symptoms and the prevention of complications. Patients seem to have a good life expectancy. The oldest GALNT2-CDG patient that has been described in the medical literature was 20 years old in 2020.