type methylmalonic acidemia with homocystinuria is a form of methylmalonic acidemia with homocystinuria (see this term), an inborn error of vitamin B12 (cobalamin) metabolism characterized by megaloblastic anemia, lethargy, failure to thrive, developmental delay, intellectual deficit and seizures. The disease is Methylmalonic acidemia with homocystinuria type cblF (Orphanet rare-disease nomenclature entry Orphanet_79284). Also known as: CblF defect, Cobalamin F defect, Combined defect in adenosylcobalamin and methylcobalamin synthesis, type cblF, Lysosomal membrane cobalamin transporter deficiency, Methylmalonic aciduria with homocystinuria, type cblF.