Methylmalonic Aciduria (MMA)


Methylmalonic Aciduria (MMA) is an autosomal recessive metabolic disorder where the body is unable to process certain proteins and fats properly. The methylmalonic acidemias are organic acidemias caused by an enzymatic defect in the metabolism of four amino acids (methionine, threonine, isoleucine and valine). This results in an abnormally high level of acid in the blood (academia) and body tissues. The severity of symptoms varies widely, ranging from mild neurological disturbances to metabolic crisis.

Diagnosis of Methylmalonic Aciduria

The condition is diagnosed during newborn screening via the heel prick test taken 48-72 hours after birth.


1:50,000 – 100,000 estimated worldwide.

Treatment for Methylmalonic Aciduria

Treatment of methylmalonic acidaemia involves dietary modification to restrict the intake of isoleucine, valine, threonine and methionine and a supplement with lysine-free, low-tryptophan amino acid mixtures to ensure supply of the other amino acids essential for optimal health. During periods of illness, fasting and infection, aggressive treatment is initiated to prevent the body breaking down its own energy stores. This is done by limiting protein intake while giving glucose, additional fluids and increased supplementation of carnitine . In some cases, also using dialysis to reduce ammonia levels and correct metabolic acidosis. Vitamin B12 supplementation improves metabolic control and reduce the risk of complications in those with a deficiency in this co-factor. One should avoid long periods of fasting.

Support Links & Materials

Organic Acidurias Handbook

OA Fruit and Veg Counting Lists

OA General Protein Counting Lists