Abstract
The natural history of the inherited MMAs depends partly on the location of the biochemical defect. Patients with defective synthesis of cobalamin cofactors who are responsive to vitamin B12 generally have a later onset of illness and a better long-term outcome than those with a defective methylmalonyl-CoA apo-mutase. Most vitamin B12-responsive patients have received the cofactor by IM injection. For the past 5 years, we have managed a child belonging to the cobalamin A class of MMA with oral therapy. The child presented in the neonatal period with keto-acidosis and was initially treated with IM vitamin B12. At age 9 months, she was switched to oral cyanocobalmin, 30 mg every 2-4 weeks. Her current regimen is 5 mg × 6 doses given over 72-84 hours every 2 weeks. Peak and trough B12 levels are 5000-10000 pg/ml and 900-2000 pg/ml. With oral B12, the level of urinary methylmalonate decreases from a pretreatment mean of 9.74 to a posttreatment mean of 3.57 mg/mg creatinine. Protein intake has been 2-2.5 g/kg/d throughput. In addition to satisfactory biochemical control, the child has shown good general health, no episodes of significant acidosis and a normal psychomotor development. Her height and weight are at the 3rd %ile. Our results demonstrate the feasibility of oral treatment with vitamin B12 in patients with this form of MMA.
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