Prenatal Therapy of a Patient with Vitamin-B12-Responsive Methylmalonic Acidemia

Abstract

Methylmalonic acidemia due to deficient synthesis of 5′-deoxyadenosylcobalamin was discovered in a mid-term fetus by culture of amniotic-fluid cells. Elevated concentrations of methylmalonic acid were also found in amniotic fluid and maternal urine. Treatment during the last nine weeks of gestation with large doses of vitamin B₁₂ given to the mother reversed the increasing maternal excretion of methylmalonic acid, which was 23 μg per milligram of creatinine at 31 weeks' gestation. Just before delivery, the mother was excreting 5 μg, two to three times normal.