has material basis in germline mutation in CD320 methylmalonic acidemia methylmalonic acidemia due to transcobalamin receptor defect https://www.malacards.org/card/methylmalonic_acidemia_due_to_transcobalamin_receptor_defect https://www.malacards.org/card/methylmalonic_aciduria_transient_due_to_transcobalamin_receptor_defect GARD:0016481 DOID:0060741 UMLS:C4749905 Methylmalonic aciduria due to transcobalamin receptor defect is a rare metabolite absorption and transport disorder characterized by a moderate increase of methylmalonic acid (MMA) in the blood and urine due to decreased cellular uptake of cobalamin resulting from decreased transcobalamin receptor function. Patients are usually asymptomatic however, screening reveals increased C3-acylcarnitine and MMA in plasma. Serum homocysteine levels may vary from normal to moderately elevated and retinal vascular occlusive disease, resulting in severe visual loss, has been reported. methylmalonic acidemia caused by mutation in CD320 Orphanet:280183 CD320 methylmalonic acidemia methylmalonic acidemia, TCbIR type methylmalonic aciduria due to transcobalamin receptor defect MONDO:0013341 MEDGEN:1670056 OMIM:613646 methylmalonic acidemia, TCb1R type inborn disorder of cobalamin metabolism and transport