Methylmalonic acidemia

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| ICD10 = | ICD9 = | ICDO = | OMIM = | MedlinePlus = 001162 | eMedicineSubj = neuro | eMedicineTopic = 576 | MeshID = |Methylmalonic acidemia ("MMA"), also called methylmalonic aciduria, is an autosomal genetic disorder affecting branched-chain amino acids. It is a classical type of organic acidemia.Methylmalonic acidemia is diagnosed in the early neonatal period, presenting progressive encephalopathy and secondary hyperammonemia. The disorder does not always result in death, if kept under control.

Causes

Genetic

The inherited form of methylmalonic acidemia causes a defect in the metabolic pathway where methylmalonyl-coenzyme A (CoA) is converted into succinyl-CoA by the enzyme methylmalonyl-CoA mutase.Vitamin B12 is also needed for the conversion of methylmalonyl-CoA to Succinyl-CoA. Mutations leading to defects in vitamin B12 metabolism or in its transport frequently result in the development of methylmalonic acidemia.

Nutritional

A severe nutritional deficiency of vitamin B12 can also result in methylmalonic acidemia. Methylmalonyl CoA mutase requires vitamin B12 to form succinyl-CoA. When the amount of B12 is insufficient for the conversion of cofactor methylmalonyl-CoA into succinyl-CoA, the buildup of unused methylmalonyl-CoA eventually leads to methylmalonic acidemia. This diagnosis is often used as an indicator of vitamin B12 deficiency in serum.http://www.biology.arizona.edu/biochemistry/problem_sets/b12/04t.html
Vitamin B12 deficiency - The methylmalonic aciduria connection

Genotypes

  • - cblA type
  • - cblB type
  • - cblC type
  • - cblD type
  • - cblF type
  • - cblH type
  • - mut type


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