Methylmalonic acid

What the risks are:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations:

Two enzymes are involved in the conversion of propionyl CoA (formed from amino acid metabolism) to methylmalonyl CoA. In addition, biotin and cobalamin are needed as cofactors. Inherited deficiencies of the necessary enzymes cause metabolic ketoacidosis requiring protein restriction and treatment with bicarbonate in the neonatal period.

Normally methylmalonic acid and its precursor (propionic acid) are found in very small amounts in body fluids because methylmalonyl CoA is converted to succinyl CoA, which is further metabolized to produce energy or is involved in the synthesis of porphyrins. When methylmalonyl CoA builds up to an abnormal level, an enzyme that converts it to methylmalonic acid becomes active.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.