An adult patient with methylmalonic aciduria due to defective cobalamin synthesis (CblA) responsive to vitamin B
12 presented suddenly with severe visual impairment ascribed to optic atrophy followed by a fatal multiorgan failure and lactic
acidosis but low methylmalonic acid in plasma and urine. Multiple deficiency of oxidative phosphorylation was found in the
patient’s liver. We suggest that patients with B
12-sensitive methylmalonic aciduria who have a milder clinical course should be carefully monitored for long-term complications.
Communicating editor: Ivo Baric
Competing interests: None declared
References to electronic databases: Methylmalonic aciduria (MMA): OMIM 251000, 277400, 251100 (CblA), 277410 (CblD), 251110 (CblB), 277380, 606169. Adenosylcobalamin:
EC 2.7.7.62. Methylmalonyl-coenzyme A mutase (MUT): EC 5.4.99.2. Citrate synthase: EC 2.3.3.1. Succinate-CoA ligase (GDP-forming):
EC 6.2.1.4. Succinate-CoA ligase (ADP-forming): EC 6.2.1.5. Succinate dehydrogenase (ubiquinone): EC 1.3.5.1. Fumarate hydratase:
EC 4.2.1.2. ATP citrate synthetase: EC 2.3.3.8. Pyruvate dehydrogenase: EC 1.2.4.1. Pyruvate carboxylase: EC 6.4.1.1. Nucleoside-diphosphate
kinase: EC 2.7.4.6.
Presented at the Annual Symposium of the SSIEM, Lisbon, Portugal, 2–5 September 2008.