Also known as MAN2B2 Deficiency
MAN2B2 Congenital Disorder of Glycosylation A rare, inherited condition caused by abnormal proteins disrupting glycosylation. In the single reported case, symptoms manifested in infancy, including recurrent infections, vasculitis, arthritis, thrombotic stroke, chronic diarrhea, cardiac and eye abnormalities, facial dysmorphism (abnormal difference in structure), speech and developmental delays, hepatomegaly (enlarged liver), and pectus carinatum (protruding breastbone).
Symptoms
MAN2B2-CDG is an extremely rare inherited condition. There is only one individual with MAN2B2-CDG published in medical literature and the affected individual developed signs of the condition during early infancy. The disorder can lead to immunodeficiency or immune dysregulation, with recurrent infections (for example respiratory infections, fungal or viral infections). Additionally, in the reported individual, the disorder presented with vasculitis (inflammation of the blood vessels), arthritis (inflammation of the joints) and a thrombotic stroke (a blood clot in the vessels of the brain) during the first years of life. Chronic diarrhea may lead to a failure to gain weight and grow at the expected rate (failure to thrive). Other features may include cardiac abnormalities, hepatomegaly (enlargement of the liver), visible abdominal veins, hyperextensible skin, pectus carinatum (the chest bone point outwards), strabismus, distinct facial features, developmental delay, including speech delay, and an abnormally small head (microcephaly).
Laboratory investigations can show immunological and hematological abnormalities (abnormalities of the immune system and the components of the blood). In case of inflammation of the blood vessels and the joints, inflammation markers, and also rheumatoid factor as an indicator for autoimmunity, may be elevated.
Diagnosis
The glycosylation of transferrin, which is often used as a screening method for CDG, is normal in MAN2B2-CDG. However, the analysis of sugar chains attached to proteins in the blood (glycan profiling) can detect the disorder, which can be done by different methods in blood and fibroblasts. Genetic testing is needed to confirm the diagnosis. Individuals with MAN2B2-CDG have two faulty copies of the MAN2B2 gene.
Treatment and Prognosis
To date, there are no curative treatment options available for MAN2B2-CDG. However, bone marrow transplantation has led to improvement of immunological symptoms in the reported patient. All other treatment is aimed at the management of symptoms and the prevention of complications.
Since the only reported patient diagnosed with MAN2B2-CDG is still young (eight years old when the case was published in 2019), long-term prognosis is difficult to predict.