methylmalonic acidemia due to transcobalamin receptor defect

Methylmalonic acidemia due to transcobalamin receptor defect is a rare disorder affecting how the body absorbs and transports vitamin B12. Because of a decrease in the function of the transcobalamin receptor, there is a moderate increase of methylmalonic acid (MMA) in the blood and urine. In most cases, people with this condition do not show obvious symptoms at first. Screening tests often reveal increased levels of C3-acylcarnitine and MMA. In some instances, serum homocysteine levels may be normal or moderately elevated. There have also been reports of retinal vascular occlusive disease, which may lead to severe visual loss in affected individuals.

Most people with this condition are asymptomatic, meaning they do not show clear symptoms. However, laboratory tests may show increased levels of methylmalonic acid and C3-acylcarnitine in the blood. In some cases, moderate changes in serum homocysteine levels are seen and there have been reports of severe visual loss caused by blockages in the blood vessels of the retina.

The condition is caused by a defect in the CD320 gene, which leads to decreased function of the transcobalamin receptor. This receptor is important for the uptake of vitamin B12 (cobalamin) into cells. The reduced cellular uptake of cobalamin causes the metabolic changes observed in affected individuals.

Information about treatment is currently limited for this condition.

Many people with this condition do not experience symptoms and it is often found through routine screening. However, because complications, such as retinal vascular occlusive disease leading to visual loss, have been reported, the outlook may vary among individuals.

Information about current research and future directions is currently limited for this condition.